CORVALLIS, Ore. -- Oregon State University quarterback Sean Mannion is expected to be out for up to a month after surgery to repair a torn meniscus.

Mannion injured his left knee during the No. 10 Beavers' victory over Washington State on Saturday. He will be week-to-week after what was considered a successful surgery Wednesday.

He could be back in time to play in the team's last four games, including the Civil War game against Oregon on November 24.

Click for Oregon State's 2012 schedule

Backup Cody Vaz will start for the undefeated Beavers when they play a nonconference game against BYU this weekend. It will be his first start since high school

Oregon State vs. BYU: Vaz gets 1st start since high school

Mannion threw for 270 yards and a touchdown in Oregon State's 19-6 victory over the Cougars Saturday. He apparently injured the knee on a handoff but did not leave the game.

Following the victory, Oregon State jumped into the Top 10 of the AP rankings for the first time since 2001, when the Beavers went to the Fiesta Bowl. The team has not opened a season with 5 wins since 1939.

Mannion was averaging 339.5 yards passing a game, second in the Pac-12 and sixth in the nation. He has thrown for 1,358 yards with seven touchdowns and four interceptions so far this season.

Related:OSUclimbs to No. 10 in APpoll

More: Beavers defeat WSU

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