LOS ANGELES (AP) — Southern California knows what it has to do to win at No. 13 Notre Dame, but another injury will make the task that much harder.

"I think our offense is going to do what they do," safety Chris Hawkins said. "I think it's up to us to stop the run."

The No. 11 Trojans are preparing to play without starting nose tackle Josh Fatu. Coach Clay Helton said Wednesday that Fatu was not expected to be cleared from a concussion he suffered in a car accident in time to play against the Fighting Irish.

Fatu has seven tackles for loss and five sacks, ranking second on the team in both categories.

Fatu's absence leaves Brandon Pili, a freshman who will be playing in his third career game, to deal with an experienced and capable Notre Dame offensive line that has been dominant in run blocking. Notre Dame is rushing for 308 yards per game, and its per-carry average of 6.90 yards ranks third among FBS teams.

Helton liked how Pili played in a 28-27 win over Utah, especially in giving inside linebacker Cam Smith the freedom to make plays.

"He really stepped up big time for us," Helton said. "He just holds the point of attack. When you have a big man holding that gap where there's two offensive linemen having to double-team, who ends up having a great game? Cam Smith. You look at 16 tackles, that means the nose tackle is doing his job."

Still, the Utes rushed for 169 yards. Hawkins said the defense was missing assignments in the first half, but played better as the game went on. The redshirt senior understands that similar breakdowns will result in long runs by quarterback Brandon Wimbush and running back Josh Adams.

The backfield pairing essentially has Notre Dame playing option football. The defense has to focus on Adams, who has rushed for 776 yards and five touchdowns. That allows Wimbush to keep the ball for big gains. Play-action can get linebackers and the secondary to overcommit, creating chances for explosive plays in the passing game.

"He's their best player on offense to me, along with their line," Hawkins said of Adams. "I expect them to get the ball to him early, try to make us honest and then try to throw some shots over our heads."

How Wimbush plays will likely determine which team keeps its aspirations of reaching the College Football Playoff alive for another week. Wimbush has one more completion (69) than rushing attempts (68) this season, which reflects his willingness to run and the overall efficiency of the Notre Dame offense.

However, in Notre Dame's 20-19 loss to No. 3 Georgia, Wimbush completed half of his 40 pass attempts for 210 yards and had one net yard rushing.

Putting the game on Wimbush's arm would seem to be the best approach, provided USC has enough healthy defenders to take away the run game.

Outside linebacker Porter Gustin will miss his fifth consecutive game with biceps and toe injuries. Defensive lineman Rasheem Green was held out of practice as he continues to deal with a sprained ankle.

"We certainly are missing our guys, but as a coordinator you look at what they do and what we have and formulate a game plan," defensive coordinator Clancy Pendergast said.

The level of concern is at the point that freshman defensive lineman Jay Tufele practiced with the first team. USC wants to redshirt Tufele this season, and the five-star recruit had been working on the scout team until this week.

Helton said Tufele wouldn't play against Notre Dame expect in an emergency because of injuries, but it reflects the level of concern with the depth on the defensive line.

Said Helton: "We're a little light."

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