Kei Nishikori ( 錦織 圭 Nishikori Kei , [ɲiɕikoꜜɾi kei] ; born 29 December 1989) is a Japanese professional tennis player, currently ranked world No. 20 by the Association of Tennis Professionals (ATP).  He is the only male Japanese tennis player ever to be ranked inside the top 5 in singles, and first reached his career-high singles ranking of world No. 4 in March 2015.
He has won 11 singles titles and was runner-up at the 2014 US Open,  making him the first male player representing an Asian country to reach a Grand Slam singles final. He also reached the semifinals at the US Open in 2016. He also became the first man from Asia to qualify for the ATP World Tour Finals and reached the semifinals in 2014 and 2016. 
Nishikori was born in Matsue in Shimane Prefecture, Japan. His father, Kiyoshi, is an engineer, and his mother, Eri, is a piano teacher. He has an older sister, Reina, who graduated from college and works in Tokyo.  He began playing tennis at the age of five. He first won the All Japan Tennis Championships for Kids in 2001, and graduated from Aomori-Yamada High School. Nishikori moved to Bradenton, Florida to join the IMG Academy in 2004 at 14 years of age.  His pastimes include football, golf, reading, and listening to music.  Nishikori was previously coached by Brad Gilbert and Dante Bottini, but has been coached by former world No. 2 Michael Chang since January 2014.
Nishikori won the 2004 title at the Riad 21 Tournament in Rabat, Morocco, and was a boys' singles quarter-finalist at the 2006 Junior French Open ; he partnering Emiliano Massa to win the boys' doubles title at that tournament.  Nishikori won the 2007 Luxilon Cup held at the 2007 Sony Ericsson Open by defeating Michael McClune.
As a junior, he compiled a 73–37 win/loss record in singles and 53–31 in doubles, achieving a combined ranking of No. 7 in the world in July 2006. 
Nishikori began the year in March with a wildcard entry to the Kyoto Challenger tournament in Kyoto, Japan, where he lost to Australian Robert Smeets in the round of 32 and just failed to qualify for the doubles tournament.  In May, Nishikori qualified for the ITF Futures event in Mazatlán, Mexico, where he was victorious in the men's singles.
A finalist in two USTA Pro Circuit events, Nishikori lost to Donald Young in Little Rock, Arkansas and Alex Bogomolov, Jr. in Carson, California. He partnered with Young to win the doubles title at Little Rock. At the Sony Ericsson Open in Miami, Nishikori paired with triple French Open champion Gustavo Kuerten, but the two were defeated in the first round. Nishikori served as a hitting partner for Roger Federer at Wimbledon.
After his ATP main draw debut in Los Angeles, Nishikori qualified for the Indianapolis Tennis Championships in July. He beat Alejandro Falla in the first round to record his first ATP main-draw win. He followed that up with a three-set win over Michael Berrer, the eliminator of seventh seed Robby Ginepri, to advance to his first ATP quarterfinal. Although he lost to Dmitry Tursunov in two sets, Nishikori became the youngest player to reach the quarterfinals at Indianapolis since Boris Becker in 1985.
Later that month, Nishikori headed to Washington, D.C. for his third career ATP event. He defeated Teymuraz Gabashvili in the first round before falling to Julien Benneteau in the second. He qualified for the China Open in Beijing, losing in the first round to Ivan Ljubičić. In October, Nishikori received a wildcard entry to the AIG Japan Open Tennis Championships in Tokyo, where he lost in the first round to Zack Fleishman. He participated in the tournament's draw ceremony and was honored with an award from the Tokyo Sports Writers Club. Nishikori finished the year representing Japan at the Asian Hopman Cup competition in Bangkok, Thailand.
2008: First ATP title
Nishikori started the year by reaching the semifinals of the Miami challenger tournament. He then entered the Delray Beach tournament as a qualifier ranked world No. 244. He gained entrance to the main draw by defeating Nicolás Todero and Alex Bogomolov, Jr.. In the first round, he defeated Florian Mayer due to a retirement in the second set. In the second round, Nishikori defeated Amer Delić, another qualifier. In the quarterfinals, he won against Bobby Reynolds. In the semifinals, he upset Sam Querrey. In the final, Nishikori upset top seed James Blake in three sets to become the first Japanese man in nearly 16 years to win an ATP event. 
Nishikori lost in the first round of the Miami Masters to the Spanish player Albert Montañés. He faced James Blake again, this time at the River Oaks International tournament in Houston, Texas in the first round, but Kei lost in two sets. He went out in the third round of the 2008 Queen's Club Championships against Rafael Nadal in just over two hours. Facing the world No. 2, Nishikori played well in the match and showed promise. His first Grand Slam appearance at the 2008 Wimbledon Championships on 23 June 2008 ended in a first-round forfeiture to French player Marc Gicquel. Suffering from an abdominal muscle strain, Nishikori retired after the second set. In August, he entered the Beijing Olympics on a wildcard.  There, he lost in the first round to Rainer Schüttler of Germany.
Nishikori made his debut at the US Open, defeating 29th seeded Juan Mónaco in the first round. He cruised to the third round, after downing Croatian Roko Karanušić. On 30 August 2008, he became the first Japanese player to reach the round of 16 at the US Open in 71 years, when he beat fourth seed David Ferrer in five sets in what was considered one of the tournament's major upsets.  He lost his chance, however, to compete in the quarterfinals when he was beaten by 17th seed Juan Martín del Potro in straight sets.
Nishikori was given a wildcard for the Stockholm Open, where he made it to his second ATP level semifinal of the year, despite playing with a knee injury. He received a walkover in his quarterfinal match against Mario Ančić, who had to withdraw due to illness. In the semifinals, he was beaten by fourth seed Robin Söderling.
2009: Injury season
Nishikori made a disappointing start to the season, losing to Jürgen Melzer in the first round of the Australian Open. On 25 March, Nishikori was named 2008 ATP Newcomer of the Year and became the first Asian player to win the award.  He withdrew from the French Open, Wimbledon, and the US Open because of an injured right elbow.
Kei made his comeback after his injury of the previous year. After receiving a wildcard at Delray Beach, he was beaten in the first round by Benjamin Becker. Kei returned to the Challenger tour later in April with great success, reaching quarterfinals at both Baton Rouge and Tallahassee events, followed by a victory at the Savannah Challenger over Ryan Sweeting in the final. On 15 May 2010, he won the Sarasota open by defeating Brian Dabul, in three sets.
Nishikori played in his first French Open. He rebounded from two sets down to defeat Santiago Giraldo of Colombia in the first round but he lost his second match against Novak Djokovic. He lost to Richard Gasquet in the first round of the 2010 Aegon Championships. At Wimbledon, he played second seed Rafael Nadal in the first round and lost in straight sets.
At the U.S. Open, the Japanese No. 1 met Marin Čilić in the second round. Nishikori ousted the 11th seed in 5 sets to advance to the third round, his best Grand Slam tournament showing in 2010.
In the 2011 Australian Open, Nishikori reached the third round, defeating Fabio Fognini and Florian Mayer along the way. His run was ended in the third round by ninth seed Fernando Verdasco. After the third-round appearance in Melbourne, his ranking rose to No. 70.
At the first two ATP Masters Series events of the year, Nishikori suffered a first-round loss at Indian Wells and a second-round loss in Miami. Nishikori then reached his second final at the 2011 U.S. Men's Clay Court Championships. He was defeated by American wildcard Ryan Sweeting.
At Roland Garros, Nishikori lost in the second round to Sergiy Stakhovsky. He faced Lleyton Hewitt in the first round at Wimbledon, but lost in four sets. Nishikori then retired in his first-round match against Flavio Cipolla at the US Open.
At the Shanghai Masters, Nishikori reached his first Masters 1000 semifinal. He defeated Robin Haase, fourth seed Jo-Wilfried Tsonga, and Santiago Giraldo, in the first three rounds. In the quarterfinals, Nishikori upset 12th-seeded Alexandr Dolgopolov in straight sets. He lost to No. 2 Andy Murray in his first Masters 1000 semifinal. He reached a career-high of world No. 30, breaking the previous Japanese mark of No. 46, set by Shuzo Matsuoka in July 1992. 
In the Swiss Indoors Basel tournament Nishikori defeated an ailing world No. 1 Novak Djokovic to reach the final, coming back from a 4–5, 0–30 deficit in the second set. The win was only Djokovic's fourth loss of the season, second loss in a completed match, and first loss of a completed match on a non-clay surface.  Nishikori was defeated in the final by Roger Federer. On the heels of the victory, Nishikori was granted special exemption into the 2011 BNP Paribas Masters and achieved a ranking of world No. 24.
2012: First Major quarterfinal and second ATP title
Nishikori started the season at the Brisbane International, where he lost in the second round to Marcos Baghdatis. At the 2012 Australian Open, Nishikori came back from a set down to defeat sixth seed Jo-Wilfried Tsonga to reach the quarterfinals of the Australian Open, where he was then defeated by fourth seed Andy Murray. Nishikori was the first Japanese male player to reach the quarterfinals of the Australian Open in 80 years. 
In Toronto, he lost his first match (after a first-round bye) to Sam Querrey. He did better in Cincinnati, making it to the third round before being defeated by Stan Wawrinka, who ended up a semifinalist in the event. Nishikori had also lost to Wawrinka in the quarterfinals in Buenos Aires in February.
On 7 October, eighth seed Nishikori won the Rakuten Japan Open in Tokyo against sixth seed Milos Raonic of Canada in three sets to win his first ATP 500 series title and second career ATP Tour title, lifting his world ranking from world No. 17 to a career-high of world No. 15. Nishikori's win was historic as he became the first Japanese man to win the Japan Open in its 41-year history. 
2013: Third ATP title
Nishikori started the year by playing the Brisbane International and reached the semifinals before retiring to Andy Murray because of a knee injury. Nishikori then reached the fourth round of the Australian Open before falling to fourth-seeded David Ferrer. Nishikori was bothered by a nagging knee injury throughout the match. Nishikori then won his third career title in the U.S. National Indoor Championships by defeating Feliciano López in straight sets. Seeded fifth, Nishikori finished the tournament without dropping a set in taking the winner's check, and moved up six ranking spots from No. 22 in the ATP rankings to No. 16.
In 2013 US Open first round, Nishikori lost to a lower-ranked opponent, this time to world No. 179 Dan Evans in straight sets.
2014: Career breakthrough
Nishikori made it to the fourth round in the Australian Open, but was dismissed by Rafael Nadal in straight sets without much trouble. He defended his title at the U.S. National Indoor Tennis Championships in Memphis, defeating Ivo Karlović in the final. He then played at the Masters 1000 event in Miami, where he was seeded 20th. Nishikori saved four match points before defeating 4th seed David Ferrer and advanced to the semifinals with a three-set win against 5th seed Roger Federer. Because of a left groin injury, he gave 2nd seed Novak Djokovic a walkover in the semifinals. He withdrew from Japan's Davis Cup quarterfinal against the Czech Republic.  Nishikori returned to action at the end of April, in Barcelona, winning the final against Santiago Giraldo of Colombia in two sets.
On 10 May Nishikori made history by reaching the final of Madrid Open, his first Masters 1000 tournament final. Nishikori beat David Ferrer in three sets in the semifinal, and faced world No. 1 and defending champion Rafael Nadal in the final. Nishikori won the first set and led by a break in the second, but Nishikori sustained a back injury while leading 4-2 and was forced to retire at 3-0 in the 3rd set having lost 7 games in a row.  The result saw him achieve a career-high #9 in ATP singles ranking.  Nishikori lost in the first round of the French Open to Martin Kližan in three sets.
Nishikori bounced back from the French Open first round loss in the grass court season by reaching the semifinals of the 2014 Gerry Weber Open before losing to Roger Federer in straight sets. Nishikori participated in the Wimbledon Championships and made it to the fourth round after surviving a tight 5-setter against clay-court specialist Simone Bolelli, but eventually lost in the fourth round to Milos Raonic, despite winning the opening set. Nishikori opened his hard-court season by participating in the Citi Open. He reached the quarterfinals only to be beaten by Richard Gasquet for the fifth time in his career in straight sets.
Nishikori reached his first Grand Slam final at the 2014 US Open. He beat Wayne Odesnik, Pablo Andújar, Leonardo Mayer and then world No. 6 Milos Raonic in a marathon five-set match that lasted until 2:26 am, tying the record for late finishes at the US Open en route to the quarter-finals.  In the quarter-finals, he scored a rare upset over Australian Open champion Stan Wawrinka, who had thus far dominated their meetings to ensure that he would regain a top ten ranking. He also became the first Japanese man in 81 years to reach the semifinals at a Major since Jiro Sato in 1933 French Championships (now French Open).  Nishikori then defeated world No. 1 Novak Djokovic in the semifinals to become the first Asian man ever to reach a Grand Slam tournament final. (As reference, an American male tennis player of Asian descent Michael Chang reached the final of Grand Slam to win French Open at the youngest age of Grand Slam history, and the finalist to be Runner up in both US Open and Australian Open.)  In the final, Nishikori lost to Marin Čilić. Nishikori's run at the US Open saw his singles ranking improve to world No.8.
Nishikori began the Asian Swing by entering the Malaysian Open as first seed and won for a third season title, beating Julien Benneteau in two sets. Nishikori then went on to participate in the Rakuten Japan Open and won the title for the second time defeating Milos Raonic in the final. However, in the Shanghai Rolex Masters, he later suffered a first round loss to Jack Sock in straight sets. Nishikori then played in the BNP Paribas Masters and reached the semifinals, defeating Tommy Robredo, Jo-Wilfried Tsonga and David Ferrer, each in three sets. However, he was ousted by Novak Djokovic in straight sets. This semifinal appearance guaranteed his berth for his ATP World Tour Finals debut. 
In his first Year-End ATP Finals, Nishikori defeated Andy Murray and David Ferrer, but was defeated by Roger Federer in straight sets. With this result, he progressed through to the semifinals and faced Novak Djokovic, losing in three sets, thus ending the year at a career high world No. 5.
2015: Career high ranking
Nishikori began the 2015 season by participating in the 2015 Brisbane International and reached the semifinals before being beaten by Milos Raonic in 3 tight-set tiebreaks. He reached the 2015 Brisbane International doubles finals with his partner Alexandr Dolgopolov but lost in straight sets. Nishikori equalled his best record yet in the Australian Open by reaching the Quarterfinals for the second time in his career, dropping only 2 sets along the way, but he was beaten in straight sets by defending champion Stan Wawrinka. In February, Nishikori won his eighth singles title and became the first ever player to win the Memphis Open three times in a row, beating Kevin Anderson in straight sets in the final.
He next participated in the 2015 Abierto Mexicano Telcel and reached the final, losing only a set to Kevin Anderson in the semifinals. By reaching the final, he earned enough ATP ranking points to move into a new career high world ranking of No. 4.  However, he lost to David Ferrer in straight sets in the final. During the March Masters, he reached the fourth round of the 2015 BNP Paribas Open for the first time in seven appearances but was upset by Feliciano López in straight sets in the fourth round. In the 2015 Miami Open, he defeated Mikhail Youzhny, Viktor Troicki and David Goffin all in straight sets losing only a total of 10 games to reach the quarterfinals. However, he was upset by an in-form John Isner in straight sets.
Nishikori began his clay-court season at the 2015 Barcelona Open Banc Sabadell where he reached the final after beating Teymuraz Gabashvili, Santiago Giraldo, Roberto Bautista Agut and Martin Kližan. He successfully defended his title by beating Pablo Andújar in the final in two sets to win his ninth career title on the tour. At the 2015 Mutua Madrid Open, Nishikori was granted a first-round bye and proceeded by defeating David Goffin in three tough-sets in the second round. He reached the semifinals after beating Roberto Bautista Agut and David Ferrer in straight sets respectively. He then lost to Andy Murray in the semi-finals and his ranking dropped to 6th as a result of failing to defend his points from the final in 2014.
Nishikori was given a tough draw at the 2015 Italian Open but managed to reach the quarterfinal after beating Jiří Veselý and Viktor Troicki, both in straight sets. He faced world No. 1 Novak Djokovic in the QF and lost in three sets. Nishikori opened his French Open campaign by defeating both Paul-Henri Mathieu and Thomaz Bellucci in straight sets to advance to the third round. He advanced to the 4R for the second time in his career after his third round opponent, Benjamin Becker, withdrew due to a right shoulder injury. Nishikori became the first Japanese man to reach the quarterfinals of the French Open in 82 years by beating Teymuraz Gabashvili.  He then played home favorite Jo-Wilfried Tsonga, but eventually lost in five set.
Nishikori opened his grass-court season by participating in the Halle Open where he reached the semifinals, only to retire in his match against Andreas Seppi down 1–4 in the first set due to his calf injury which he attained in his quarterfinal match. Nishikori decided to play Wimbledon, and he reached the second round by beating Simone Bolelli in five sets for the second straight year but then withdrew from his second round match against Santiago Giraldo, due to his calf injury acting on him again during his first round match. 
Nishikori opened his hard-court season by competing at the 2015 Citi Open defeating James Duckworth, Leonardo Mayer, Sam Groth, and Marin Čilić en route to the final where he beat John Isner in three tight sets to capture his third title of the year and 10th title overall. At the 2015 Rogers Cup, he reached the semifinals without losing a set and defeated Rafael Nadal for the first time in eight tries in the quarterfinals. He lost to Andy Murray in the semifinals in straight sets. He withdrew from the Cincinnati Masters citing fatigue and hip injury, which affected his semifinal match against Murray the previous week. He lost in the first round of the 2015 US Open to Benoît Paire.
Nishikori started the Asian Fall by participating in his hometown tournament, Rakuten Japan Open, where he reached the semi-finals, including victories over Borna Ćorić, Sam Querrey and Marin Čilić. He was upset in his semi-final match by unseeded Benoît Paire. He reached third rounds of the Shanghai Rolex Masters before losing to Kevin Anderson. He then played in the BNP Paribas Masters. However, he retired in the third round match against Richard Gasquet due to an abdominal injury. 
Nishikori qualified for the ATP World Tour Finals for the second straight year in a row, clinching eighth place.  He defeated Tomáš Berdych, but lost to Novak Djokovic and Roger Federer. He failed to qualify for the semifinals, finishing in third place in his group.
2016: Olympic Bronze Medal and more
Nishikori began the season ranked No. 8. In January, he entered the Brisbane International as the No. 2 seed where he advanced to the quarterfinals with a bye and a straight sets win over Mikhail Kukushkin, but was eventually upset by seventh seed Bernard Tomic in three sets. At the Australian Open, Nishikori was seeded seventh. He began with victories over Philipp Kohlschreiber, Austin Krajicek and Guillermo García-López before beating ninth-seeded Jo-Wilfried Tsonga to reach his third Australian Open quarterfinal, where he lost to Novak Djokovic. Nishikori next competed at the Memphis Open where he was seeded first and was the three-time defending champion. Nishikori received a bye into the second round and advanced to the semifinals without dropping a set. In the semifinals, Nishikori beat Sam Querrey in three sets and later beat young American Taylor Fritz in straight sets to win his fourth straight Memphis title and his 11th ATP title overall. He joined Jimmy Connors as the only four-time winners of the event. 
During the March Masters, Nishikori reached the quarterfinals in the Indian Wells Masters for the first time in his career after defeating Mikhail Kukushkin, Steve Johnson in straight sets and saving a match point against ninth seed John Isner in Nishikori's serve in the third set. He lost to fourth seed Rafael Nadal in straight sets. Nishikori improved his feat by reaching the quarterfinal again in the Miami Open by beating Pierre-Hugues Herbert, Alexandr Dolgopolov and Roberto Bautista Agut in straight sets. He then reached the semifinals of the tournament for the second time in his career after saving five match points and beating Gaël Monfils in a comeback three-set match. He then reached his second final in a Masters 1000 after dismantling Nick Kyrgios in straight sets.  He lost to then world No. 1 Novak Djokovic in the final in straight sets.
For the 5th consecutive year, Nishikori did not play in Monte Carlo and instead turned his focus to defending his Barcelona Open Banc Sabadell title. He reached the final without losing a set, but lost in straight sets to resurgent nine-time champion Rafael Nadal in the final. He followed his good run by reaching the semifinals in the Mutua Madrid Open, beating Fabio Fognini, Richard Gasquet for the first time in 7 meetings and rising teenage star Nick Kyrgios. He lost in the semifinal to Novak Djokovic in straight sets despite a close 2nd set. Nishikori then replicated his Madrid run by reaching the semifinals of the Italian Open for the first time after beating Viktor Troicki in the opener in three sets, followed by wins over Richard Gasquet and Dominic Thiem in straight sets. He lost in the semifinal against world Novak Djokovic in a marathon 3 hours three-setter despite winning the first set 6–2 and managed to pull off a tiebreak in the third set. He later participated at the French Open but unfortunately lost to an in-form Gasquet in the fourth round in 4 sets. Nishikori began his grass season at the Halle Open, but retired in the 2nd round due to a hip injury. His next tournament was at Wimbledon, where he retired in the fourth round against Marin Čilić, once again due to injury.
With Murray, Federer and Nadal absent, Nishikori was seeded 3rd for the Rogers Cup Masters in Toronto. After beating Grigor Dimitrov and Stan Wawrinka in the quarterfinals and semifinals respectively, Nishikori then lost to Djokovic in straight sets in the finals, going 0–5 so far in the season against the Serb. Nishikori then participated in the Rio Olympics, where he reached the semis before being defeated by World No. 2 Andy Murray in straight sets. However, he later acquired the bronze medal after he defeated a strained Rafael Nadal 6–2, 6–7, 6–3, becoming the first Japanese man to win a tennis medal in 96 years.
Nishikori nearly replicated his 2014 US Open run by reaching the semifinals of the US Open, defeating Benjamin Becker, Karen Khachanov and Nicolas Mahut respectively in four sets, followed by a straight sets fourth-round win against Ivo Karlović, and a massive 5 set victory over world No. 2 Andy Murray in the quarterfinals that lasted nearly 4 hours; this was arguably his biggest victory since the 2014 US Open. After leading by a set and a break against eventual champion Stan Wawrinka in the semifinals, a clearly fatigued Nishikori lost in 4 sets, hence ending his U.S hardcourt season with a finals and semifinals run in the Canadian Open and the US Open respectively.
After an indifferent Asian swing season where he retired in his home tournament, the Rakuten Japan Open, Nishikori returned to action again in Basel, where he was the No. 3 seed. He enjoyed a successful tournament there, but lost to Marin Čilić in the finals.
Nishikori next represented Japan in the Davis Cup Play-Off against Ukraine and played in the doubles rubber alongside Yūichi Sugita, winning the match in straight sets, giving Japan an unassailable 3–0 lead to promote his country back into the 2017 Davis Cup World Group.
Nishikori made his third successive appearance at the year-end championships after becoming the fifth player to qualify for the 2016 ATP World Tour Finals.  He won his first match, upsetting third seed, Stan Wawrinka in straight sets 6–2, 6–3 before losing his other two round-robin matches to Andy Murray and Marin Čilić respectively, both in three sets. Having done enough to nevertheless make the semifinals however, he was then defeated by a resurgent Novak Djokovic in straight sets, ending his season with a singles ranking of world No. 5 for both the second time in his career and in the past three years as well.
2017: Wrist injury and out of the top 20
Nishikori began the year by reaching the finals of Brisbane, beating Wawrinka along the way, before falling to champion Grigor Dimitrov. In the Australian Open, after defeating Andrey Kuznetsov in five sets in the first round, Kei beat his next two opponents in straight sets. His run ended in another five-set match to eventual champion Roger Federer. 
Unfortunately, Nishikori withdrew from the US Open in Cincinnati with a right wrist problem and subsequent scans revealed a tear in one of the tendons.  Soon after that, he announced that he would miss the rest of the season.  As a result of his extended absence, following the conclusion of Paris he fell to World No.22, his lowest ranking since January 2012 and his first time out of the top 20 in the rankings since March 2014.
Nishikori made his Davis Cup debut for Japan in April 2008 in the Asia/Oceania Zone Group I semifinal against India in New Delhi. He was 18 years and 104 days old, the youngest player to play for Japan.  He played the singles rubber on the first day, but lost to Rohan Bopanna in five sets. He then defeated Mahesh Bhupathi in a dead rubber to record his first Davis Cup match win. To date, Nishikori has compiled a 19–3 win/loss record overall (17–3 in singles and 2–0 in doubles).
In the 2014 Davis Cup World Group first round in Tokyo, Japan defeated Canada 4–1, and Nishikori had a hand in three Japan victories in the tie. He beat Peter Polansky and Frank Dancevic in the singles rubbers, and teamed up with Yasutaka Uchiyama for a victory in doubles over Dancevic and Daniel Nestor. Japan advanced to the quarterfinals in the World Group for the first time,  but Nishikori missed the quarterfinal against Czech Republic due to a left groin injury. 
Nishikori represented Japan at his maiden Olympics in Beijing 2008. He competed in the singles competition from ITF places spot.  There, he lost in the first round to Rainer Schüttler of Germany in three sets.
At the London 2012 Olympics, Nishikori competed in the singles and doubles competitions, partnering Go Soeda. In the singles, being 15th seed, he reached the quarterfinals, knocking out Bernard Tomic, Nikolay Davydenko, and fourth seed David Ferrer on the way. He became the first Japanese man to reach the quarterfinals since Takeichi Harada in the 1924 Paris Olympics.  However, his run ended by eighth seed Juan Martín del Potro of Argentina. In the doubles, Nishikori and Soeda were eliminated in the first round by Switzerland's defending champions Roger Federer and Stan Wawrinka.
Fresh from his Rogers Cup finals appearance in Toronto, Nishikori represented Japan at the Rio 2016 Olympics, where he was seeded 4th. In the semi-final he lost to Andy Murray and faced Rafael Nadal for the Bronze medal match which he won in 3 tight sets. It was the first tennis medal for Japan in 96 years.
Nishikori vs. Wawrinka
Nishikori and Wawrinka have met 8 times, with both player tied in their head-to-head 4-4. Wawrinka won both of their first two meetings in 2012, in the 3rd Round of Cincinnati Masters and in the quarterfinal of Buenos Aires respectively. Nishikori recorded his first win against Wawrinka at the quarterfinal of the 2014 US Open in a thrilling tight five-sets match which saw Nishikori later became the eventual finalist of the tournament.
They met in another Grandslam quarterfinal, this time at the 2015 Australian Open. Wawrinka beat Nishikori in 3-straight-sets.
They met 3 times in 2016. Nishikori won 2 of their 3 meetings in 2016. They both qualified for the 2016 ATP World Tour Finals and were drawn in the same group. Nishikori defeated Wawrinka in the round robin match.
Nishikori won their most recent meeting at the early season of 2017, in Brisbane.
Nishikori vs. Raonic
Nishikori and Raonic have met 7 times, with Nishikori leading their head-to-head 5–2. They met once in 2012, 4 times in 2014 and twice during the 2015 season. At their first meeting in the 2012 Rakuten Japan Open final, Nishikori won it in 3 sets. Their first meeting in 2014 was at the Madrid Masters with Nishikori winning in two tiebreak sets. In Wimbledon 2014 4R, Raonic scored his first win against Nishikori beating him in four sets to advance to the Quarterfinals. They met again in the US Open 4R where the match tied the all-time latest finish for a match at the US Open with Nishikori prevailing in five tight-sets which lasted 4 hours and 19 minutes. They had a rematch of their 2012 final in the Rakuten Japan Open 2014 final where Nishikori won again in 3 sets.
In 2015, the duo first met at the Brisbane International with Raonic prevailing in 3 tight-set tiebreaks. This was followed later on in the same year in the Davis Cup where Nishikori won in another epic five-setter to keep Japan's hopes for a quarterfinal place alive with the score tied again at 2–2.
Nishikori vs. Ferrer
Nishikori and Ferrer have met 14 times, with Nishikori leading 10–4. They met for the first time in the 2008 US Open with Nishikori registering his first win over a top-10 player, beating David Ferrer in a five-set thriller as a teenager. They next met again from 2011–2013 with Ferrer winning 3 times in straight sets and Nishikori winning only once in the Olympics at 2012 in three sets. However, in 2014, Nishikori showed that his 2–3 deficit head-to-head encounter against Ferrer was just the beginning and thrashed the Spaniard in each of the 4 encounters in 2014. They first met in 2014 in the Miami Masters with Nishikori beating Ferrer in 3 tight-sets after saving 4 match points to progress to the QF. They next had an epic encounter at the Madrid Open with Nishikori beating Ferrer in another tight 3-setter to progress to the final of a Masters 1000 for the first time in his career. Their next 2 encounters were in the BNP Paribas Masters and the ATP World Tour Finals where Nishikori again defeated the Spaniard in 3 sets.
In 2015, Ferrer had a remarkable start to the season but was beaten in the Australian Open by Nishikori in a dominant straight sets victory. However, Ferrer ended his losing streak to Nishikori in the Abierto Mexicano Telcel where he beat Nishikori in straight sets in the final. In Madrid, in the quarterfinals, Nishikori took revenge and beat him in straight sets.
Nishikori vs. Čilić
Nishikori and Cilic have met 13 times with Nishikori leading 7–6. Cilic won their first ATP World Tour meeting in 2008 at Indian Wells, beating Nishikori in straight sets in the first round. In 2010, Nishikori avenged that loss at the US Open, beating Cilic in a tough five-setter lasting almost five hours. In 2011, they met at the Chennai Open where Nishikori beat Cilic in three sets. In 2012, they encountered each other at the US Open where Cilic avenged his past US Open loss to Nishikori by beating him in four sets to progress to the 4R. In 2013, they met at the Memphis Open where Nishikori beat him in straight sets to progress to the SF and he would later go on to win the title.
In 2014, their rivalry was more intense with 3 ATP meetings. They first met in 2014 at the Brisbane International where Nishikori beat him in three sets to book his semifinal spot. They met again at the clay courts of the Barcelona Open where Nishikori dominated Cilic in another straight sets victory where he would later go on to win his first title on clay. Their most significant meeting would be at the 2014 US Open, they met in the finals after Nishikori overpowered world No. 1 Novak Djokovic and Cilic overcame world No. 2 Roger Federer in the semifinals. Their meeting in the final made the 2014 US Open the first Grand Slam where none of Federer, Nadal and Djokovic reached the final since the 2005 Australian Open. However, Nishikori was defeated in straight sets by an in-form Marin Cilic in the final.
In 2015, the pair met in the semifinals of the 2015 Citi Open, with Nishikori coming back from a set down to prevail in three, and gain a place in his 15th career final. They meet again later on in the 2015 Japan Open where Nishikori came back from a set down to defeat Cilic in three tight sets. In 2016, the duo met in the 4th round of the 2016 Wimbledon where Nishikori retired mid-match in the 2nd set after losing the first set due to a rib injury which had disrupted his grass season. They met again in the final of the Swiss Indoors, where Cilic prevailed in straight sets. Their most recent meeting came during the round-robin stage of the Year-End 2016 ATP World Tour Finals, that of which saw Cilic come from a set down to again defeat Nishikori and ultimately prevail.
Nishikori has endorsed the Wilson Wilson Burn 95; however, it is believed by racquet enthusiasts that he used an older modified Wilson nCode nTour underneath the Steam paint job. In the past, special versions of the Steam racquet have been sold by Wilson, exclusively in Japan, capitalizing on Nishikori's popularity in his home country. Most recently, in 2012 the Steam Pro was available for sale, and was advertised as having the same specifications as Nishikori's actual racquet. As of 2015, Nishikori currently uses the Wilson Burn 100. He wears Uniqlo clothing and as of the beginning of 2017 red Nike Vapor Tour shoes after having played for almost a decade in Adidas.  He is also sponsored by Nissin Foods, TAG Heuer, Fast Retailing, LVMH Moët Hennessy, Japanese financial services firm Jaccs Co.,  WOWOW, mattress topper Air Weave, EA Games,  , Delta Air Lines and Japan Airlines, in a deal which has his image emblazoned on a Boeing 777-300ER dubbed "JET-KEI".  He is often seen wearing a Cup Noodles badge on his sleeve during matches. In 2011, he filmed a commercial for Morinaga & Company's sports drink Weider in Jelly.  He also carries around a character called Mr. Saturn from the popular video game Mother / Earthbound .
With solid and consistent shots on both wings, Nishikori plays most comfortably at the baseline, using dominating groundstrokes to push his opponents around and hit winners. He can generate a lot of pace, especially on his flat backhand, while his Western forehand is accurate and consistent. However, he also has the ability to play defensively and hit consistently to wear out his opponents. Because of this, many people have commented that he has the offensive ability of Fernando González and the defensive skills of Novak Djokovic. Many critics and fellow players have said that Nishikori's two handed backhand is one of the best on the tour, on par with that of Djokovic and Murray. Under the coaching of Michael Chang, Nishikori has gained the habit of taking balls earlier without compromising consistency, reminiscent of Andre Agassi, allowing him to take time away from his opponents. Nishikori has a slightly unusual style of hitting groundstrokes on both wings, winding up the racket with a short but compact backswing, and hitting the ball right at its peak. These make his groundstrokes powerful, accurate and unpredictable due to the delayed backswing, which prevents opponents from anticipating which direction the ball will go.
He has also been praised for his return of serves, which he executes well due to his ability to take them quickly. He is known to hit winners off return of serves with strong and accurate groundstrokes.
Although his serve is not exceptionally strong, it is consistent enough to prevent opponents from easily winning points off it. He has a flat first serve that can reach speeds of up to 125 mph and employs a topspin second serve.
Grand Slam tournament performance timeline
|Grand Slam tournaments|
Grand Slam finals
Singles: 1 (1 runner-up)
|Outcome||Year||Championship||Surface||Opponent in the final||Score in the final|
|Runner-up||2014||US Open||Hard|| ||3–6, 3–6, 3–6|