USC defensive end Wes Horton is almost certainly sidelined after getting kicked in the back. An ankle sprain continues to limit end Nick Perry. And versatile Armond Armstead is playing with a sore shoulder that forced him to miss last week's game at Washington State.
Even defensive line coach Ed Orgeron is on crutches after foot surgery this week.
So, it's probably not the best time for USC's front four to face Washington's Jake Locker.
After four games against undermanned opponents, the 18th-ranked Trojans enter the heart of their schedule Saturday evening at the Coliseum against a dual-purpose quarterback who entered the season projected by some as the possible No. 1 pick in the 2011 NFL draft.
Sure, the 6-foot-3, 230-pound senior has performed below expectations. Locker's career-worst, four-for-20, two-interception performance two weeks ago against Nebraska prompted questions about whether he still ranks among the top quarterbacks in the Pacific 10 Conference, let alone the nation.
But Locker has proven that he is more than capable of leading his team to victory with a dynamic, clutch performance.
Just turn back the clock to Sept. 19, 2009. That's when Locker made like Joe Montana, rallying the Huskies in a near-flawless game-winning drive to upset the Trojans in a Pac-10 opener at Seattle.
On Saturday, Locker goes up against a USC defensive line that also has underperformed to date.
Orgeron and Coach Lane Kiffin trumpeted the unit throughout spring practice and training camp, calling it the strength of a team looking to rebound from last season's disappointing 9-4 finish.
The line has been tough of late against the run. However, pressure on quarterbacks has been inconsistent, sometimes absent. The group also has failed to force many fumbles.
"We're not a dominant group like we want to be," Orgeron said. "But we're going to get there."
USC's defensive line has been evolving since the end of spring practice, when starting nose tackle Christian Tupou learned that he needed season-ending knee surgery.
In July, reserve end Malik Jackson bolted for Tennessee, taking advantage of an NCAA exemption that allowed juniors and seniors to transfer without sitting out a season because USC was hit with a two-year bowl ban.
Perry, a freshman All-American who had eight sacks last season, suffered a high ankle sprain in training camp and sat out the opener at Hawaii. Armstead was hurt against Virginia, aggravated the injury against Minnesota, and sat out last week's rout at Pullman, Wash.
Horton, who blocked a punt against Washington State and got his team-high third sack, left the game after Perry accidentally kicked him.
Tackle Jurrell Casey has been the only starter to avoid injury, which has affected Orgeron's preference for rotating three ends and three tackles.
Defensive linemen have accounted for eight of the Trojans' 11 sacks. USC has six interceptions.
"We haven't put enough pressure on the quarterback," Casey said. "If we did, the [defensive backs] would have way more interceptions and we'd have more sacks."
It won't get easier against Locker.
Kiffin, who coached last season at Tennessee, compared him to former Florida quarterback Tim Tebow.
"He can run the ball, he can throw the ball, he's extremely fast and then he's powerful at the point of contact when you do finally tackle him," Kiffin said.
USC wasted no time getting to Locker last season, Casey sacking him and forcing a fumble on the Huskies' first offensive play. Washington recovered the ball, but the Trojans kept Washington's offense mostly in check until the final drive.
Even that started well for the Trojans, Perry sacking Locker for a 12-yard loss that put the Huskies at their 22-yard line with less than four minutes left.
"All I remember about that is, 'I'm trying to get the quarterback,'" Perry said. "The momentum kind of changed a little bit, but things happen and it didn't go our way."
What happened was this: Locker went off.
He regrouped after the sack and completed all four of his passes, including 21- and 19-yard strikes to receiver Jermaine Kearse. He also ran once as the Huskies drove for a game-winning field goal.
Locker's heroics gave Steve Sarkisian a program-defining victory in his third game as coach.
"It was one of the drives that kind of helped to allow everybody to buy into everything that was going on," Locker said this week. "It kind of put a big-statement win on our season."
USC's defensive linemen are eager to return the favor.