Where did the player who replaced Trevor Knight prior to the 2015 season begin his football career?
Trevor Knight:  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. Baker Mayfield:  Mayfield began his college football career as a walk-on player for the Texas Tech Red Raiders.
Texas Tech Red Raiders