After a humbling blowout loss to Northwestern, Penn State football’s defense is under immense scrutiny.

Defensive coordinator D’Anton Lynn’s unit allowed an astonishing 413 yards on the ground on 55 carries, good for the third-worst performance by a Nittany Lions defense in program history.

Northwestern offensive coordinator Chip Kelly’s Wing-T offense gashed Penn State all night, raising questions about the Nittany Lions’ physicality and causing some reflection for Lynn.

“What surprised me was the line of scrimmage,” Lynn said. “I don’t know if we won the line of scrimmage once. We didn’t lose every time, but we didn’t win at all.”

Penn State fans aren’t used to seeing the Nittany Lions get dominated up front, with the program built on a physical, tough brand of defense dating back to the Joe Paterno days.

That standard wasn’t reflected in the team’s performance Friday night, with Penn State struggling to make plays even when players were in the right places.

“There were a lot of runs that could have been 2-, 3-, or 4-yard gains and went for 20-plus yards because of missed tackles,” Lynn said. “It was a short week, and I probably didn’t do as many tackling drills that week as we should have.”

After the first half on Friday, Lynn came down from the coaches’ booth and onto the field. In the first half, his unit gave up 24 points and 237 rushing yards, with nearly 10 yards per carry.

“It was just hard to watch from up top,” Lynn said. “It just felt better being down there while all that was going on, just to be able to talk to the guys, talk to the coaches.”

Lynn’s sideline presence in the second half didn’t spark much of a turnaround, as the unit still gave up 176 yards on the ground in the final two quarters.

This adversity is uncharted territory for Penn State, which had previously been one of the nation’s most dominant defensive teams.

Even after the loss to Wisconsin, three takeaways for Penn State earned the defense praise throughout the week.

Effort was a clear issue on Friday, however, especially in the second half, when the game seemed out of reach for Penn State. That defensive identity, or lack thereof, won’t lead to much success in the Big Ten.

“When we go out there, we have to have the same mentality. We have to have the same edge. We can’t let the scoreboard change that. We can’t let how we’re playing change that,” Lynn said. “We have to have that same attitude every snap.”

It won’t get any easier for the Nittany Lions’ defense moving forward as they prepare to face a high-powered offense in No. 19 USC on Saturday, led by head coach Lincoln Riley and quarterback Jordan Maiava.

Offenses coached by Riley are something Lynn is familiar with, having faced them in practice when Lynn was the USC defensive coordinator the previous two seasons.

“[Riley’s] tough because he doesn’t really have a playbook. He just has plays, and he’s gonna do what his guys do best,” Lynn said. “He probably has the best scheme-beaters in the country if he knows what you’re in.”

Riley has proven himself as one of the best offensive minds in college football over the past decade. He’s developed three future first-overall quarterbacks, and his offenses consistently rank among the best in the country.

USC is again near the top of the nation in offense statistically with 467.8 yards and 37.8 points per game. Lynn’s unit will have its hands full limiting the Trojans in the White Out.

“You can’t look up at the stats. They’re gonna move the ball. They’re gonna have plays,” Lynn said. “We need to be great on third down. We need to be great in the red zone, and we need to stop the run, and then don’t give them chunk plays. Make them drive all the way downfield.”