OH NO! QB SEAN MANNION OUT INDEFINITELY!!

This season has been nothing but good news for the Beavs, jumping out to a 4-0 start and soaring up the polls from nowhere to the No. 10 ranking in the nation. But a little rain must fall and it did so on Monday... Sean Mannion is out. Cody Vaz is in. Mannion, the Beavs' starting quarterback, will have knee surgery and is out indefinitely, said Mike Riley and Oregon State this afternoon.

Sean Mannion suffered the injury to his left knee on a handoff during Saturday's 19-16 win over Washington State, though Mannion continued to play.

Mannion was wearing a brace at practice on Monday but then left to meet with a doctor.

With Mannion out, Cody Vaz will now start for the 10th-ranked Beavers as they prepare to face BYU on the road Saturday.

The official release from Oregon State:

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 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.”

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.

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.