Question: Who took Trevor Knight's starting position at quarterback on the Oklahoma Sooners college football team in the 2015 season?

Context paragraphs:
1895 Oklahoma Sooners football team: The 1895 Oklahoma Sooners football team represented the Oklahoma Sooners of the University of Oklahoma during the 1895 college football season and was its first football team ever fielded.  The team completed its inaugural season with a 0–1 record.  The Sooners played their first football game in history against a town team from Oklahoma City and lost by a final score of 34–0.  This was the program's one and only season under the guidance of head coach John A. Harts, the next season he was gold prospecting in the Arctic.

1956 Oklahoma Sooners football team: The 1956 Oklahoma Sooners football team (variously "Oklahoma", "OU", or the "Sooners") represented the University of Oklahoma in the 1956 college football season.  It was the 62nd season of play for the Sooners.  The team was led by Hall of Fame head coach Bud Wilkinson.  They were led on offense by quarterback Jim Harris, and played their home games at Oklahoma Memorial Stadium in Norman, Oklahoma.

2005 Oregon Ducks football team: In 2005, Oregon had success behind senior quarterback Kellen Clemens and a new spread offense.  During a game at Arizona, Clemens suffered a broken ankle.  At that point Oregon was 8-1 (their only loss was to #1 ranked USC 45-13, the loss was vacated in 2010), and still in the hunt for a BCS game.  Oregon won their final three games and their success led them into contention for a bid to the Fiesta Bowl.  The Ducks finished the regular season with a 10-1 record, their best finish since their Joey Harrington-led, Fiesta Bowl-winning 2001–2002 team.  They finished 5th overall in the BCS ranking system, which would in many years have been high enough to earn them a bid to a BCS Bowl.  In 2005, however, there were no at-large bids available to Oregon.  Ohio State finished just ahead of the Ducks, in 4th place, guaranteeing them one of the at-large berths (although they had an inferior 10-2 record).  Notre Dame finished 6th in the BCS, also securing a BCS bid due to a pre-existing clause in the BCS contract.  Many college football fans were outraged that two teams with worse records were selected over the Ducks.  Moreover, for the second consecutive year, the Pac-10 conference had a team that finished with a one-loss season snubbed by the BCS (the Cal Bears finished 10-1 in 2004).  It was later demonstrated that Oregon drew the highest bowl ratings in college football, calling the argument that TV ratings hurt the Ducks' BCS chances into question.  The situation (and others like it in recent years) has led to more calls for a playoff system to replace the BCS, which has received widespread criticism from college football fans.  Instead of a BCS game, they were assigned to the 2005 Holiday Bowl versus the Oklahoma Sooners.  Playing without their starting quarterback, Kellen Clemens, and combined with a strong showing from the Sooners, the Ducks fell in a close game, 17-14, finishing the season tied for the second-best in school history with a 10-1 overall record (the Southern Cal game was deemed vacated by violations in 2010).

1985 Oklahoma Sooners football team: The 1985 Oklahoma Sooners football team represented the University of Oklahoma in the college football season of 1985–1986.  This year was Barry Switzer's 13th season as head coach.  The Sooners ended this season with 11 wins and a sole loss coming to the Miami Hurricanes in Norman, in a game in which the Sooners lost starting quarterback Troy Aikman for the season.  The Sooners were forced to place their trust in lightning-quick true freshman quarterback Jamelle Holieway and a physical defense featuring three All-Americans, who led them to a Big 8 Conference title and a national championship.  This was Oklahoma's sixth national championship and 34th conference championship in school history.

Trevor Knight: Trevor Knight (born October 3, 1993) is an American football quarterback for the Atlanta Falcons of the National Football League (NFL).  He played college football for the Oklahoma Sooners and Texas A&M Aggies.  After leading Oklahoma to an 8–5 record in the 2014 season, he lost the starting job in an open quarterback competition to Texas Tech transfer Baker Mayfield prior to the 2015 season.  On January 4, 2016, it was announced that Knight would transfer to Texas A&M University.

List of Oklahoma Sooners bowl games: The Oklahoma Sooners college football team competes as part of the National Collegiate Athletic Association (NCAA) Division I Football Bowl Subdivision (FBS), representing the University of Oklahoma in the Big 12 Conference.  Since the establishment of the team in 1895, OU has appeared in 50 bowl games and has a record of 29 victories, 20 losses, and one tie.  Oklahoma is one of only two schools to have appeared in all five of the BCS bowl games (2001 Orange, 2003 Rose, 2004 Sugar, 2007 Fiesta, 2009 BCS NCG), with the other being Ohio State.

List of Oklahoma Sooners football All-Americans: This is a list of Oklahoma Sooners college football players who were named first team All-Americans.  The selecting organizations for football All-Americans that the NCAA recognizes include the Associated Press, American Football Coaches Association, Football Writers Association of America, The Sporting News, and the Walter Camp Football Foundation.  The NCAA defines consensus All-Americans as players who were accorded a majority of votes at their positions by these selectors.  Unanimous All-Americans are players who were selected by all five selectors.

Baker Mayfield: Baker Reagan Mayfield (born April 14, 1995) is a college American football quarterback for the Oklahoma Sooners.  Mayfield began his college football career as a walk-on player for the Texas Tech Red Raiders.  He is notable for being the first walk-on true freshman quarterback to start a season opener at a BCS school.  Mayfield transferred from Texas Tech to Oklahoma following alleged scholarship issues and a lack of communication with coaches.  After sitting out the 2014 season due to NCAA transfer rules, Mayfield won the starting quarterback job in 2015 over Cody Thomas and incumbent starter Trevor Knight.

List of Oklahoma Sooners football seasons: The Oklahoma Sooners college football team competes in the National Collegiate Athletic Association (NCAA) Division I Football Bowl Subdivision, representing the University of Oklahoma in the Big 12 Conference.  The Sooners have played their home games at Oklahoma Memorial Stadium in Norman, Oklahoma since 1923.

Josh Heupel: Joshua Kenneth Heupel (born March 22, 1978) is the offensive coordinator and quarterbacks coach for the Missouri Tigers.  He is also a former college football player who played quarterback for the Oklahoma Sooners football team at the University of Oklahoma.  During his college playing career, he was recognized as a consensus All-American, won numerous awards, and led Oklahoma to the 2000 BCS National Championship.  Heupel became a coach after his playing career ended.  He served as co-offensive coordinator for the Oklahoma Sooners until January 6, 2015, when he was fired from his position.  He was named the assistant head coach, offensive coordinator, and quarterbacks coach at Utah State on January 23, 2015.  After one season at Utah State, he was hired at the University of Missouri under Barry Odom's new staff.

Supporting paragraphs: Trevor Knight Baker Mayfield
Answer: Baker Mayfield