Beavers must move on without QB Mannion

Perhaps the biggest surprise team in college football -- the 10th-ranked Oregon State Beavers -- are going to have to go on for an undisclosed amount of time without sophomore quarterback Sean Mannion.

Coach Mike Riley announced earlier Monday that Mannion will have knee surgery.

The news comes after the Beavers (4-0 overall, 3-0 Pac-12) have climbed into the AP Top 10 for the first time since starting the 2001 season ranked 10th.

Details of Mannion's injury were not released, though Riley said Mannion had an MRI on Sunday.

The 6-foot-5, 212-pound second-year starter was having a very strong season. Through the first four games, he had completed 107 of 169 passes (63.3 percent) for 1,358 yards and 7 touchdowns with 4 interceptions.

Mannion played the entire game in Saturday's 19-6 win over Washington State. Though it was his worst statistical performance of the season, with three interceptions.

Cody Vaz, a junior from Lodi, Calif., will step in as the starter when the Beavers travel to BYU this weekend.

The implications are obvious. While the Beavers have been a much stronger team this year on both sides of the ball, Mannion's continued development was certainly a big reason for the team's success. He had found a good rhythm with wide receivers Markus Wheaton, and Brandin Cooks and the improved running game had allowed for more play-action and opened up a lot of shots down field.

Under Mannion, the Beavers have the Pac-12's fourth-rated offense, averaging 459.5 yards per game and the league's No. 2 passing attack. Mannion, along with Arizona's Matt Scott, are the only two Pac-12 quarterbacks averaging more than 300 yards passing.

Vaz does have some playing experience, though it's limited. In 2010, he appeared in five games and completed 6 of 17 passes for 48 yards. He has no touchdowns or interceptions.

Obviously, making your first career start midseason is tough. It's going to be tougher on the road against a BYU defense that ranks third nationally in points allowed (8.8).

Injury attrition was a concern for the Beavers, who had their bye in Week 3. Their season opener against Nicholls State was postponed until Dec. 1 because of Hurricane Isaac, so Oregon State's second game of the year didn't come until Week 4.

If there is a bright side to this, it's that Riley has been very high on Vaz -- and even said during the spring that he thought Vaz was closing the gap between him and Mannion. Plus, the news comes on a Monday, meaning Vaz has the entire week to start building some chemistry with his receivers.

There are enough playmakers around Vaz that Oregon State fans shouldn't be hitting the panic button just yet. But Mannion's injury certainly puts a damper on what was starting out as a special season for the Beavers.