An already thin USC defensive line will be without its most productive rusher the rest of the way, as defensive end Anthony Lucas suffered a season-ending injury in the loss to Penn State, Lincoln Riley said Tuesday.

Lucas underwent surgery Tuesday morning to repair what Riley deemed to be “a lower extremity” injury.

Lucas left last Saturday’s game early in the fourth quarter after slipping on a pass rush. Lucas rolled into Penn State quarterback Drew Allar on the play and was called for roughing the passer. But it was Lucas who remained sitting on the field, surrounded by trainers who appeared to be tending to his ankle.

The loss is a devastating blow to a USC defense that was already struggling to pressure opposing passers. Lucas led the Trojans with 12 pressures, four more than any other USC defender.

“Hate it for Anthony because he’s really improved and had a really strong impact on our defense,” Riley said. “But he’s in a good frame of mind, we’ll be excited to get him back next year and get him rolling and build on all the progress he made. And in the meantime, it’s gonna create an opportunity for some more guys to step up.”

The problem is very few of those options are proven. Sophomore Braylan Shelby is third on the team in pressures (seven) and the most experienced pass rusher whose role should presumably increase. But Riley also pointed to freshmen such as Kameryn Fountain and Lorenzo Cowan as potential beneficiaries of Lucas’ absence.

“You rely on the development that’s been going on behind the scenes and the guys that we’ve recruited,” Riley said. “Maybe there’s some guys you thought, well, maybe their role won’t be quite as much this year or maybe they redshirt, and now, all of a sudden they’re going to have that opportunity. All of us can point to our careers to guys who became phenomenal cornerstone type players of a program who got their first shot like this.”