BOULDER, Colo. -- Rashard Ross returned the second-half kickoff 100 yards for a touchdown to break open a close game, and Taylor Kelly threw three scoring passes to tailback Marion Grice in Arizona State's 51-17 victory over Colorado on Thursday night.
Grice caught touchdown throws of 37, 16 and 20 yards from Kelly, who threw for 308 yards and five TDs with no interceptions thanks to a steady diet of successful screen passes. He also tucked it and ran for 67 yards through huge chunks of open space all night long.
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The Sun Devils (5-1, 3-0 Pac-12) will take a three-game winning streak into their showdown next week against second-ranked Oregon.
The Buffaloes (1-5, 1-2) fell to 2-1 at home in Thursday night ESPN games. They beat Stanford in 1990 and West Virginia in 2008 and trailed 20-17 in this one at the break after scoring 10 points in the final 24 seconds of the first half.
"We have a lot of momentum," Buffs coach Jon Embree said at halftime.
Not for long.
Ross took the kickoff a yard deep in his end zone and darted down the right sideline untouched, reaching the other end zone 11 seconds later to make it 27-17.
That jump-started a 31-0 second-half onslaught by the Sun Devils.
Grice's third touchdown, from 20 yards out, made it 34-17 heading into the fourth quarter.
Just before halftime, Colorado's Jordan Webb hit tight end Nick Kasa over the middle for a 23-yard TD, and Jamal Miles fumbled the ensuing kickoff at his 17. K.T. Tu'umalo recovered for Colorado and after two shots into the end zone came up empty, Will Oliver nailed a 36-yard field goal as the first half expired.
The Sun Devils struck first when Kelly threw a screen pass to Grice, who weaved his way for a 37-yard score in the first quarter. Nate Bonsu blocked Joe Mora's extra point, leaving Arizona State with a 6-0 lead.
"That's just one less point that they have," Bonsu said at halftime. "And that's huge because that could be the difference in the game."
The Buffs couldn't keep up with the up-tempo Sun Devils to make that miss matter, however.
Alex Garoutte replaced Mora after the Sun Devils' next score and kicked his 25th PAT in 25 tries, giving Arizona State a 13-7 lead following Kelly's 34-yard strike to running back D.J. Foster.
Will Sutton's 8-yard sack of Webb helped the Sun Devils force a three-and-out and the Arizona State offense needed just three plays and 61 seconds to stretch its lead to 20-7.
Keller hit Chris Coyle for gains of 30 and 18 yards, then threw a frozen rope 16-yard touchdown pass to Grice, the ball zipping just past linebacker Jon Major's helmet as he failed to turn his head.
Mora came back to kick a 38-yard field goal in the fourth quarter that made it 37-17, then kicked the extra point following Richard Smith's 31-yard touchdown catch.
The Sun Devils capped their 31-0 second-half onslaught with Cameron Marshall's 14-yard TD run with 3:34 left following Robert Nelson's interception.
That score came a couple of minutes after Buffs linebacker Brady Daigh was strapped to a backboard after injuring his neck on a tackle of backup quarterback Michael Eubank with 4:40 left in the game. Daigh was conscious and moving but was transported to a hospital for precautionary medical tests.
Colorado was already without starting tailback Christian Powell (thigh) and three defensive starters: free safety Ray Polk (ankle), linebacker Paul Vigo (foot) and cornerback Yuri Wright (concussion).
Arizona State's schedule gets tougher and, considering the Sun Devils lost six of their final seven games last season after a similar 5-1 start, this was a game they couldn't afford to look past, and they didn't.