Sean Thomas Mannion (born April 23, 1992) is an American football quarterback for the Los Angeles Rams of the National Football League (NFL). He played college football at Oregon State and was the Beavers' starting quarterback from 2011 to 2014. He was drafted by the Rams in the 3rd round of the 2015 NFL draft.
High school career
Although Mannion was born and raised in San Jose, California, Mannion attended Foothill High School in Pleasanton, California. Not only did Mannion play football, but he also played on the baseball varsity team as a pitcher in his junior and senior year and he also played on the junior varsity basketball team but never made the varsity team. As a senior, he played in 12 games and threw for 3,521 yards and 27 touchdowns, in his first year as the starter for the Varsity high school football team. He came out of high school as a 3-star recruit according to ESPN. On February 3, 2010, he signed with Oregon State University, turning down offers from San Diego State University, San Jose State University, UCLA, and Washington State University.
Mannion was redshirted as a freshman in 2010. As a redshirt freshman in 2011, he started 10 out of 12 games. He finished the season completing 305 of 473 passes for 3,328 yards, 16 touchdowns and 18 interceptions.
During his sophomore season in 2012, Mannion completed 200 of 309 passes for 2,446 yards with 15 touchdowns and 13 interceptions. 
Mannion remained the starter in 2013. On September 21, 2013, Mannion threw for five touchdown passes against Utah, tying an Oregon State University football record held by Derek Anderson. The next game, On September 28, Mannion threw for six touchdown passes against the University of Colorado, setting a new school record for most passing touchdowns in a game. Mannion finished the 2013 season leading the Beavers to a 7–6 record, including a victory in the Hawaii Bowl over the Boise State Broncos. In the final game, Mannion threw for 259 yards, giving him a Pac-12-record, 4,662 yards passing for the season.  He finished the year with 37 passing touchdowns, which was a school record. 
Remaining the starter his senior season in 2014, Mannion became the Beavers all-time leader in career passing yards and passing touchdowns during the season, passing Derek Anderson's records.   Later in the year, he became the Pac-12's all-time leader in passing yards, breaking Matt Barkley's record.   He finished the season with 3,164 yards and 15 touchdowns.
For his career, Mannion started 43 games, completing 1,187 of 1,838 passes for 13,600 yards, 83 touchdowns and 54 interceptions.
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|Ht||Wt||40‑yd dash||10-yd split||20-yd split||20‑ss||3‑cone||Vert jump||Broad|
| 6 ft 5 1 ⁄ 2 in |
| 229 lb |
|5.14 s||1.87 s||3.03 s||4.39 s||7.29 s|| 31 in |
| 8 ft 9 in |
|All values from Oregon State Pro Day |
He was selected 89th overall by the St. Louis Rams in the third round of the 2015 NFL Draft.  He started his career as the third-string quarterback behind Case Keenum and Nick Foles in his rookie year in 2015.
Mannion played his first NFL game of his career in a week 12 matchup against the Cincinnati Bengals in which the St. Louis Rams lost 31-7. He was put in the game late in the fourth quarter, taking over from starting quarterback Case Keenum. He completed 6 passes out of 7 attempts for 31 yards, posting a 85.1 passer (QB) rating.
Mannion started 2016 as the second-string backup quarterback behind the starter, Case Keenum and ahead of the 1st overall pick of the 2016 NFL Draft, Jared Goff. In the season opener against the San Francisco 49ers, Jared Goff took over as the second-string quarterback, demoting Mannion back as the third-string backup quarterback. Mannion was promoted to second-string for the final two weeks of the season. In Week 17, Mannion completed 3 of 6 passes for 19 yards with one interception after starter, Jared Goff, was subbed out of the game in a 44-6 loss to the Arizona Cardinals.
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