Muscala played for the Bucknell Bison men's basketball team for four seasons. He was the 2011 Patriot League Men's Basketball Player of the Year after leading the Bison to an NCAA Tournament appearance. In addition, he was named to the First Team All-Patriot League and AP All-American Honorable Mention in 2010-2011.  He was a 2012–13 Academic All-America selection.  He was also a 2012–13 Senior CLASS Award finalist.  Muscala also earned more hardware in 2013 as he won the Patriot League Player of the Year, Defensive Player of the Year, and First-Team All Conference honors,  becoming the first player in Patriot League history to earn Player of the Year and Tournament MVP twice. During his 2012–13 campaign, Muscala also became Bucknell's all-time leading scorer surpassing Al Leslie's 32-year record. 
NBA draft and Spain (2013–2014)
On June 27, 2013, Muscala was selected by the Dallas Mavericks with the 44th overall pick in the 2013 NBA draft. He was subsequently traded to the Atlanta Hawks on draft night,  and later joined the Hawks for the 2013 NBA Summer League.
On August 1, 2013, Muscala signed a one-year deal with Río Natura Monbús Obradoiro of the Liga ACB.  On February 25, 2014, he parted ways with Obradoiro and returned to the United States.   In 20 games for the club, he averaged 14.6 points, 7.8 rebounds and 1.1 assists per game.
Atlanta Hawks (2014–present)
On February 27, 2014, Muscala signed a multi-year deal with the Atlanta Hawks.  He made his debut for the Hawks on March 2, recording four points and five rebounds in a loss to the Phoenix Suns.  In the team's regular season finale on April 16, Muscala scored a season-high 15 points in a 111–103 win over the Milwaukee Bucks. 
In July 2014, Muscala re-joined the Hawks for the 2014 NBA Summer League. During the 2014–15 season, he received multiple assignments to the Fort Wayne Mad Ants of the NBA Development League.  On March 28, 2015, he had a season-best game with 18 points, 10 rebounds, 4 assists, 1 steal and 2 blocks in a loss to the Charlotte Hornets. 
Muscala again played for the Hawks' summer league team in 2015, averaging 9.8 points and 7.3 rebounds in six games. On February 3, 2016, he scored a season-high 12 points in a 125–86 win over the Philadelphia 76ers.  On March 26, 2016, he was presented with the Jason Collier Memorial Trophy for being the player who best exemplifies the characteristics Collier displayed off the court as a community ambassador. 
On June 29, 2016, the Hawks exercised the option for the 2016–17 season on Muscala's contract. 
On July 25, 2017, Muscala re-signed with the Hawks. 
NBA career statistics
|GP||Games played||GS||Games started||MPG||Minutes per game|
|FG%||Field goal percentage||3P%||3-point field goal percentage||FT%||Free throw percentage|
|RPG||Rebounds per game||APG||Assists per game||SPG||Steals per game|
|BPG||Blocks per game||PPG||Points per game||Bold||Career high|