ESPN.com Big 12 Offensive Player of the Year: Oklahoma QB Baker Mayfield

Baker Mayfield had a Big 12-leading completion rate of 68.6 and accounted for 42 total touchdowns, but his value to the Sooners can't be measured with just stats. AP Photo/Tony Gutierrez

A year ago, Baker Mayfield showed up to Oklahoma without a scholarship, much less the promise of a starting job.

Today, he's the ESPN.com Big 12 Offensive Player of the Year.

Why he won: Mayfield led the Big 12 with a completion rate of 68.6 percent to go along with 35 touchdown passes. He only tossed five interceptions. And on top of throwing for 3,389 yards, he rushed for another 420 yards and seven touchdowns.

Mayfield's value to the Sooners, however, can't be measured with just stats.

His unbridled confidence helped resurrect an Oklahoma program that was desperately in need of a spark after an 8-5 season in 2014. And Mayfield's knack for keeping plays alive and delivering in the clutch carried the Sooners all season.

No play more underscored Mayfield's relentlessness than his game-clinching touchdown pass at Baylor. With less than five minutes remaining, Mayfield extended the play by stepping up, jumping back and rolling right before flinging the ball off his back foot to fullback Dimitri Flowers, who wasn't even supposed to be going out for a pass. The score sealed the win for Oklahoma, and helped catapult the Sooners through November and into the College Football Playoff.

Mayfield was simply sensational all season.

Defining moment: It feels like forever ago, but Mayfield's heroics at Tennessee not only saved the Sooners, they set the tone for what kind of season Mayfield would have. Down 17-3, Mayfield essentially willed Oklahoma down the field for a pair of late touchdown drives in which he manufactured several first downs by improbably breaking tackles in the backfield to keep plays alive. Both touchdown throws came on third-and-goal. And in the first overtime, he converted a fourth-and-goal with a nifty scoring plunge. In the second overtime, he fired a strike to Sterling Shepard for what proved to be the game-winner.

The win at Tennessee was not only a defining moment for Mayfield, it was a turning point for Oklahoma as a program.

Runner-up: Through October, TCU quarterback Trevone Boykin was not only the runaway favorite to win Big 12 Offensive Player of the Year, he had begun to turn the Heisman chase into a two-man race with LSU running back Leonard Fournette. Alas, a poor performance at Oklahoma State followed by a sprained ankle knocked Boykin from his perch.

Boykin, however, still had a phenomenal season with more than 3,500 passing yards and 31 touchdowns to guide the Horned Frogs to a 10-win season even after a rash of injuries struck the squad on both sides of the ball. His game-winning touchdown pass in overtime in the downpour against Baylor was a fitting way for him to go out in his final game at Amon G. Carter Stadium.