Oregon State coach Mike Riley was faced with a delicate decision after the Beavers' first loss of the season last weekend — whether to start Cody Vaz or Sean Mannion at quarterback against Arizona State on Saturday night.

Mannion was the team's starter at the beginning of the season, leading the Beavers to wins in their first four games and averaging 339 yards in passing. But the 6-foot-5 sophomore hurt his left knee and required surgery. Vaz, a junior who hadn't started since he'd been in Corvallis, took over and led the Beavers to two straight wins.

Then came Washington. Mannion returned as starter but threw four picks before he was replaced by Vaz, who fell just short of pulling off a Beavers comeback in a 20-17 loss last Saturday.

That put Riley in a difficult spot.

"Obviously, it's one of those things that's not easy," Riley said. "You look at the integrity of the competition and you try to make a decision for the team that's right this minute. We think Cody's playing a little bit better right now and deserves the start."

Mannion was gracious, telling Vaz he was "behind him 100 percent." He also vowed to get better.

"It's a little disappointing, but I'm confident in myself, and I've got a ton of confidence in my teammates," Mannion said. "You know, this is a team. It's not about any one player."

Overall, the 13th-ranked Beavers (6-1, 4-1 Pac-12) were banged up as they looked toward rebounding from the Washington loss against the Sun Devils. Receiver Markus Wheaton suffered a concussion after a hard hit in the loss to the Huskies, but should return against the Sun Devils. Running back Storm Woods had a sore left knee but said he's probably play.

Oregon State will likely be without cornerback Jordan Poyer, who has five interceptions this season and is tied for second nationally. Poyer has a sprained right knee and didn't practice this week, although Riley wouldn't definitively rule him out for Saturday night's game.

Arizona State is expected to see the return of defensive tackle Will Sutton, who returned to practice this week. Sutton, considered one of the top defensive players in the Pac-12, injured his right knee early in the Sun Devils' 43-21 loss to Oregon on Oct. 18 and hasn't played since.

The loss to the Ducks was the first of two straight at home for Arizona State (5-3, 3-2) after a three-game winning streak. The Sun Devils fell 45-43 to UCLA last weekend, but they are still in the thick of the Pac-12 South race behind USC and the Bruins.

"Our guys had a great spirit and a great attitude, just like they have had for me all year long. I know they are going to go up there for me and play hard and prepare to win and that is what we have to do," Sun Devils coach Todd Graham said. "That is the great thing about things in the south right now, it is wide open and no one is sitting any better than we are."

Arizona State, just a win away from bowl eligibility, has a three-game losing streak in Corvallis, although the Sun Devils defeated the Beavers 35-20 last year in Tempe.

Whether the Beavers play Vaz or Mannion shouldn't make much of a difference for Arizona State, which is ranked third in the nation in pass defense, allowing opponents an average of just 148.8 yards per game. Conversely, the Beavers are ranked 15th in the nation for pass offense with an average of nearly 312 yards a game.

In fact, the game figures to be a battle of defenses. Arizona State and Oregon State are ranked first and second, respectively, in the Pac-12 for overall defense. The Sun Devils are allowing just 322 yards a game, while the Beavers are allowing an average of 344.1.

Vaz is averaging 201 yards passing per game in his two-plus appearances, with four touchdowns and no interceptions. He said he has some goals against Arizona State, and they have nothing to do with any competition with Mannion.

"I just want to make the most of it. I'm going to do whatever it takes to win," he said earlier this week. "We can't try to force anything offensively, we've got to convert on third downs — that's kind of been our Achilles' heel in the last few games, not staying on the field. We just have to move the ball down the field, convert on third down, and we'll be fine."