Key Reasons Behind USC Trojans' Struggles on Defense

USC's Defense Struggled Against Illinois

The Trojans were without star safety Kamari Ramsey against Illinois, and the Fighting Illini quarterback Luke Altmyer exposed USC's lack of depth in the secondary, finishing with 328 passing yards. Meanwhile, the Trojans' defensive line struggled as Illinois averaged 4.9 yards per carry.

Altmyer was not pressured by the USC defense as Illinois' offensive line only allowed one sack and no quarterback hurries. Trojans cornerback Brandon Conley contributed USC's only tackle for loss in the game as the Trojans defensive line was knocked back throughout the game against Illinois.

In the secondary, USC defensive coordinator D'Anton Lynn mainly relied upon safeties Bishop Fitzgerald and Christian Pierce as well as cornerback Marcelles Williams to fill Ramsey's absence in the defensive backfield.

Trojans linebackers Eric Gentry and Desman Stephens II impressed, but USC's eight missed tackles were the most of any game for the Trojans so far in 2025.

As Big Ten competition continues to ramp up, will USC's defense be able to stop the physical offenses from No. 20 Michigan, No. 21 Notre Dame, and No. 2 Oregon?

Lincoln Riley's Assessment

In the week after USC's first loss of the season, Trojans coach Lincoln Riley was asked about the defensive line's slow start against Illinois:

"I think we had some opportunities to make some impactful plays early on in that game. We missed some opportunities to do that both in the run game and in the show game. I think that’s one of those things, not just defensive line, just as a team one of those things. We had a great opportunity to start fast as a team and we didn’t do that on either side. When you do that against a good team on the road you’re going to be in for a dog fight like we were after that," Riley said.

"We’ve built that group up enough that we have high expectations for it and that’s part of having high expectations. We expect every time that we’re on the field to feel the presence and it really wasn’t until later on in the game that we started feeling that a little bit more…We weren’t awful there, certainly weren’t to the standard that we expect out of our defensive front," the USC coach continued.

Riley and his coaching staff have a bye week before hosting Michigan in the Los Angeles Memorial Coliseum on Oct. 11.