Coach Lane Kiffin repeatedly praised USC's defensive line this spring, but it got thinner on Wednesday with the announcement that senior starting nose tackle Christian Tupou will miss the 2010 season with knee injury.
Tupou, who started 21 games over the past two seasons, tore a ligament in his left knee during the spring game on Saturday.
"It's unfortunate that it happened, but I'm okay," Tupou said in a statement. "I'll deal with it. It's part of the game. I'm down, but I'm not out because I can come back in 2011. Through training and rehab, I see a brighter light at the end of the road."
Tupou has yet to use his redshirt season, so if he could return in 2011 as a redshirt senior.
He had 25 tackles and four tackles for a loss in 2009 and earned honorable mention All-Pac-10 honors. A political science major, he will graduate next week and will begin graduate study in the fall.
With Tupou out, DaJohn Harris and Hebron Fangupo will compete for the starting job, defensive line coach Ed Orgeron said in a text message to ESPN.com's Bruce Feldman. Derek Simmons was listed behind Tupou on the post-spring depth chart.