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Quarterback Sean Mannion will start for No. 7 Oregon State against Washington on Saturday, less than three weeks after undergoing a surgical procedure on his left knee.

Mannion missed two games after he was hurt in an Oct. 6 victory over Washington State in Seattle. The 6-foot-5 sophomore was injured on a handoff, and an MRI revealed the need for surgery to repair the meniscus in his knee.

Cody Vaz started in Mannion's place and Oregon State has remained unbeaten, rising to 6-0 overall and 4-0 in the Pac-12.

"It was difficult. Cody has played well and Sean has played well," coach Mike Riley said Tuesday. "I just kind of took it back a little bit further to the initial competition. Sean had played four games and played well so we decided to go with him. But it was not easy."

It was surprising when Mannion was cleared to play last week in advance of Oregon State's game against Utah. But because Vaz had started the week practicing with the first unit, he was designated as the starter and Mannion was listed as the backup. The Beavers beat the Utes 21-7.

Vaz completed 16 of 26 passes for 174 yards against Utah. But the 6-foot-1 junior really wowed the week before in his debut as a starter against BYU, throwing for 332 yards and three touchdowns.

There were questions about Vaz because he hadn't started a game since high school and had last appeared for the Beavers in the 2010 season, when he played in five games and completed six of 17 passes for 48 yards.

Not anymore.

"The one thing we feel good about is our quarterback situation," Riley said, "because now Cody's got some experience. He's won a couple of games. We would never even blink about playing him."

Mannion has thrown for 1,358 yards with seven touchdowns and four interceptions this season. He is sixth on Oregon State's career list with 4,686 yards.

Before he was hurt, Mannion was averaging 339.5 yards passing a game to rank second in the Pac-12 and sixth in the nation.

One of four team captains this year, Mannion is a classic drop-back passer with a calm demeanor and a good grasp of the fundamentals, the product of growing up the son of a high school coach.

Last season as a redshirt freshman, Mannion unseated junior starter Ryan Katz, who had started the 2010 season for the Beavers. Katz has since transferred to San Diego State.

Oregon State's third option at quarterback is redshirt freshman Richie Harrington.

The Beavers have rebounded from finishing 3-9 last season to opening 6-0 this season. Oregon State has not opened a season 6-0 since 1907.