EVANSTON-Northwestern's defense and linebacking corps will face a challenge on Saturday at Penn State unlike any they have seen before this season.

After two rocky campaigns, it looks like head coach James Franklin has the Nittany Lions back on track and firing on all cylinders. Penn State is undefeated and ranked 11th in the country, boasting an offense that is putting up nearly 40 points per game.

If the Wildcats, 1-3 after losing three straight home games, are going to stand any chance of competing with the Nittany Lions in Happy Valley, they will need their linebackers to be at their absolute best.

It has been a tumultuous start for the linebacker group, and the defense, this season. They were solid in the second half against Nebraska to secure a win, and held Miami (Ohio) to 17 points, albeit in a loss. On the other hand, they struggled mightily against Duke and Southern Illinois, allowing 31 points each time.

Linebackers coach Tim McGarigle is focused on week-by-week improvements for his group, and for the defense as a whole.

"As a full defense, we have to get one week better every week," McGarigle said. "And we feel like we have every week.

"We feel like we're playing a little bit better every single week from a linebacking corps and from a defensive perspective, and we have to continue to do that."

McGarigle is specifically targeting some timeless issues as points of improvement before the matchup with Penn State.

"We've talked about doing a better job stopping the run and tackling, that's the essence of defense," McGarigle said. "You're never going to arrive at being done with doing that, or working on that.

"That's something that you'll always have to work on and continually strive to get better at. Stopping the run, defeating blocks, tackling; that's going to be the answer until the end of football."

The composition and strategy of the group has shaped up a bit differently than projected at the end of last year, and after the transfer portal dust settled. Last year, three linebackers were in the top five of Northwestern's top tacklers: Chris Bergin (132), Bryce Gallagher (90) and Peter McIntyre (68).

This year, the Wildcats are using a lot of two-linebacker looks within defensive coordinator Jim O'Neil's 4-2-5 "star," or nickel alignment. Gallagher is leading the team in tackles with 38, and junior Xander Mueller is tied for second with safety Jeremiah Lewis with 25. The next linebacker on the list is Greyson Metz at No. 13, with seven.

Linebacker isn't like the defensive line, where players get rotated in and out regularly. But a couple names that Northwestern fans thought might make an impact have been absent most of the season.

Pittsburgh transfer Wendell Davis Jr., who registered 27 tackles in three starts and eight games for the Panthers in 2021, was expected by many to play a pivotal role this season. But Davis hasn't been healthy and has yet to suit up for the Wildcats, according to an NU spokesperson who didn't know a timetable for his return.

Sophomore Mac Uihlein, a four-star prospect from Lake Forest who was the No. 1 recruit in Illinois in 2021, has a couple tackles this year and saw some time at linebacker against Nebraska. But he has been limited to special teams in three games since.

"[Mac plays] on special teams and you earn your reps during the practice week and through special-teams performance," McGarigle said. "They're continually getting better and you know, they'll get in when we feel that it's the best thing for the defense."

For the immediate future, it looks like Gallagher and Mueller will continue to anchor the second level, with Metz involved when the Wildcats go to a 4-3 front. Safety Rod Heard II is usually in the lineup instead of Metz when they employ their nickel package.

Mueller has had to step up in his first year as a starter to lead the second level of the defense, alongside Gallagher.

"It's definitely been a grind, but I love every part of it," Mueller said.

He knows that he and the linebackers have to work to do, and isn't afraid of self-evaluation. Like the defense as a whole, he's fixated on getting better incrementally.

"I have a lot of ways that I can improve," Mueller said. "Physicality is definitely one of them, and tackling.

"Overall, doing my job and helping the team in the way that the coaches plan for it. They put a great scheme out for us, so I try to execute my job."

Head coach Pat Fitzgerald has emphasized the turnover battle all season long, and Mueller has answered the call with a team-leading two interceptions. Turnovers are crucial to Northwestern's defensive identity.

As a team, the Wildcats are minus-5 in turnover margin, which ranks 121st in the nation. Their lone victory against Nebraska came when they won the turnover battle 3-1. Since then, it's been 9-2 in favor of the opposing teams in their three losses.

"One of the biggest focuses is punching the ball out," Mueller said. "Getting to the ball and getting it off tips is definitely huge, and punching the ball out. That stuff is a point of emphasis for us every week."

Northwestern is going to need some of that emphasized turnover luck this week against Penn State. But it figures to be difficult: the Nittany Lions have just one turnover this season, an interception in the season opener against Purdue. They have played three clean games since and rank eighth in the nation with a plus-8 turnover margin.