CORVALLIS, Ore. (AP) Oregon State quarterback Sean Mannion is out indefinitely after injuring his left knee during the No. 10 Beavers' victory over Washington State on Saturday.
Backup Cody Vaz will start for the undefeated Beavers when they play a nonconference game against BYU this weekend.
Mannion had his knee in a brace at practice on Monday. Coach Mike Riley says an MRI has indicated the 6-foot-5, 212-pound sophomore quarterback will require surgery.
The specific nature of Mannion's injury was not released.
Mannion threw for 270 yards and a touchdown in Oregon State's 19-6 victory over the Cougars. 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.
Mannion was averaging 339.5 yards passing a game, second in the Pac-12 and sixth in the nation.
Mannion has thrown for 1,358 yards with seven touchdowns and four interceptions this season.
Vaz, a 6-foot-1, 198-pound junior, played in five games in the 2010 season, completing six of 17 passes for 48 yards. He did not appear in any games last season for the Beavers.
Release from OSU Media Services
Corvallis - Oregon State University sophomore quarterback Sean Mannion will miss an undetermined amount of time after being diagnosed with a left knee injury Monday. The sophomore sustained the injury on a handoff during the No. 10 Beavers' 19-6 win over Washington State last Saturday at Reser Stadium.
Mannion, from Pleasanton, Calif., is second in the Pac-12 Conference for passing, averaging 339.5 yards per game. He has completed 107 of 169 pass attempts with seven touchdowns and already ranks sixth for career passing at OSU with 4,686 yards. He has taken every snap for the Beavers in the last 14 games.
Mannion will be replaced in the starting lineup by junior quarterback Cody Vaz from Lodi, Calif. Vaz has appeared in five games during his career, all in 2010 as a redshirt-freshman, completing 6 of 17 pass attempts for 48 yards. Vaz's backup will be redshirt freshman quarterback Richie Harrington from Westlake Village, Calif.
"Cody is a good quarterback; he's been preparing for this for a long time," head football coach Mike Riley said. "He's had a ton of reps; in fact he almost had as many as Sean did during fall camp. Cody knows what we are doing, he gets rid of the ball fast and he's accurate."
The Beavers return to action Saturday at BYU at 12:30 p.m. PDT in a game being televised to a regional audience by ABC. OSU is 4-0 for the first time since 2002 and seeks its first 5-0 start since 1939.