Tyler Gaffney took 15 months off of football, but once he returned to the Stanford offense, he shook off the cobwebs like he shakes off would-be tacklers.

This is a guy who lives for the two-yard gain, for the extra surge, for taking nothing and turning it into something.

“If a play is supposed to be minus-two and it ends up plus-two for him, that’s a big play for him,” said coach David Shaw, whose Cardinal head to Tempe to take on Arizona State in today’s Pac-12 championship game at Sun Devil Stadium. “When a play is supposed to be four yards and he gets 12, he loves those. He runs with such determination and leg drive and body lean.”

Those traits helped him on the baseball field, where he took a brief sojourn to the minor leagues before returning to Stanford for one more season.

“He came back because he loves the school, he loves his teammates, he loves this team, and he loves football,” Shaw said. “He had an idea that we still had a chance to be a good team and he wanted to be a part of that. He’s become a huge part of that.”

Gaffney told Sports Illustrated’s Stuart Mandel before spring ball that the combination of “getting your degree, being part of this team, being able to play football, is outweighing staying on the baseball team.”

It wasn’t an easy choice — after being selected in the 24th round by the Pittsburgh Pirates in 2012, he batted .297 for Single-A State College (Pa.) and finished with a .483 on-base percentage — but it’s a choice that has paid off.

He capped off a 1,485-yard regular season with a 189-yard performance in a 27-20 win over Notre Dame, then picked up an All-Pac-12 second-team honor. He finished with 17 rushing touchdowns and 100-yard performances in six of his final seven games. The other? Just 95 yards and a score in a 63-13 thumping of Cal in the Big Game.

“For him, the last seven weeks or so, you’ve just seen unbelievable determination,” Shaw said. “Not everything is fought perfectly, but he has a lot of pride in not having negative plays.”

Gaffney had played most of his college career as an afterthought, a complementary player in a Stanford backfield that had grown to be among the most dominant in the game.

In 2009, he shadowed Toby Gerhart, who ran for 1,871 yards and 28 touchdowns. In 2010 and 2011, he backed up Stepfan Taylor, as Taylor ran for 1,137 yards as a sophomore and 1,330 yards as a junior. Gaffney had 704 yards combined in those two seasons.

But he showed flashes, just like he did early this year, with 136 yards in Stanford’s first two games, before a three game sub-100 streak.

The first team to hold him under 100? Arizona State, which limited him to 87 yards on 18 carries in a 42-28 loss on Sept. 21.

“He’s a very seasoned, mature, veteran player,” Arizona State coach Todd Graham said. “He brings it every single play. First quarter or last quarter. You can tell he gets stronger as the game goes on.

“He’s gotten stronger as the season’s gone on.”

That he has.

Gaffney has rushed for 1,023 yards in Stanford’s final seven regular-season games, with games including the 189-yard outburst against the Fighting Irish, 171 in a 24-10 win over UCLA, 158 in a 20-17 loss to USC, 157 in a 26-20 win over Oregon, and 145 in a 20-12 win over Oregon State.

“He’s just a consistent warrior,” Graham said. “He’s the key, and the key for him is the guys in front of him. The best offensive line we’ve played all year long, hands down. The best-coached team we’ve played against. Very innovative — they don’t get near enough credit for what they do offensively, and the innovation they use in the run game.”