Don Ryan, Associated Press
Oregon defender Boseko Lokombo, right, grabs Oregon State quarterback Sean Mannion as he attempts to pass during the first half of an NCAA college football game in Eugene, Ore., Saturday, Nov. 26, 2011.

While BYU has lost Taysom Hill for the season due to a knee injury, No. 10 Oregon State, which visits Provo on Saturday, is dealing with its own quarterback changes.

Starter Sean Mannion is out with a knee injury, and Cody Vaz will replace him in the lineup.

"One of the best young quarterbacks in the country, Mannion’s improvement this season has played a huge role in OSU’s 4-0 start (3-0 Pac-12)," wrote Lindsay Schnell of the Oregonian. "His best performance of the season came two weeks ago when he threw for a career-high 433 yards and three touchdowns in a come-from-behind 38-35 win at Arizona. A year after taking his lumps as a freshman, Mannion had blossomed in Riley’s offense this season, and had established himself as one of the best quarterbacks in the Pac-12. Through four games he had completed 107-of-169 attempts for 1,358 yards and seven touchdowns, an average of almost 340 yards per game. Now the focus shifts to Cody Vaz, a 6-foot, 198-pound junior who hasn’t taken a live snap in more than two years"

Oregon State's defense is looking forward to playing BYU's style of offense.

BYU quarterback Riley Nelson talks about his health and returning to the field this week.