STATE COLLEGE, Pa. -- Linebacker U finds itself in a nightmare situation at linebacker.

All three Penn State starters are nursing injuries -- Nyeem Wartman-White is out for the season with a torn ACL -- and all three could be gone for an extended period. Although James Franklin doesn't discuss injuries unless they're season-ending, outside linebacker Brandon Bell was on crutches Saturday and middle linebacker Jason Cabinda missed the last two games with a cast on his left hand.

Maybe no position was thinner this season. On Aug. 4, Franklin essentially admitted as much: "That's going to be an important position from a depth perspective, but we feel good about the first-line guys."

One analyst rated that first line as one of the preseason's 10 best in the nation. Now, that line might be entirely gone for Saturday's matchup against Michigan -- leaving two sophomores and a walk-on in their place.

"It is what it is," Franklin said Saturday, referring to the defensive injuries. "We just have to keep working through, keep grinding, and keep developing those guys."

He really has no other choice. Troy Reeder, an ESPN.com selection on last year's freshman All-B1G team, bolted in the offseason to play with his younger brother at FCS school Delaware. That left just eight scholarship linebackers on the roster -- three of whom are now injured, one who was a former walk-on and mainly plays special teams, one not even listed on the depth chart, and another in Cameron Brown, who's a true freshman.

That means only two remaining scholarship linebackers -- sophomores Manny Bowen and Jake Cooper -- have any real game experience.

"It's the 'next man up' mentality, and we are all going to rise to the occasion," Cooper said Tuesday. "This is a tremendous opportunity for us, and we're going to grow as a unit. We're going to get the job done."

Bowen, Cooper and current walk-on Brandon Smith -- the three linebackers who saw the most snaps Saturday -- have said all the right things over the past week. But they're in an unenviable position.

The young defensive line has shown cracks the first few weeks, and the run defense was exposed in Week 2 against Pitt. Even with two of their three starting linebackers in that game, the Nittany Lions still surrendered 226 rushing yards in the first half. That was the most allowed by Penn State at halftime in at least 12 years.

The defense rebounded admirably against Temple and the backup linebackers played well, but the Owls are nothing like Saturday's opponent in Michigan. Like Pitt, Michigan boasts one of the top offensive lines in the conference and its two top backs are averaging a combined 6.4 yards a carry.

Even if Franklin didn't panic at the podium, there's no hiding the fact he knows this defense could be in trouble. He announced Tuesday that safety Koa Farmer was moving back to outside linebacker, and he hinted that Farmer could play at the position as early as this weekend.

Likewise, Bowen or Cooper might be asked to play in the middle when Farmer comes in for Smith. Even if the two sophomores are accustomed to playing outside.

"Now we're in a situation where it's not just about what positions they understand," Franklin said. "It's also about getting the best three guys on the field. So it will be interesting to see how this plays out this week."

Smith is a smart, hard-working linebacker, but even he seems to know he's not the long-term answer here. He never before played with the first team and even acknowledged Tuesday, "As far as measurable things, I'm pretty average."

There's potential at linebacker; Bowen and Cooper could make future All-B1G teams. But the talent here is also young; it's inexperienced. It's limited. It hasn't played much together.

And it's about to be tested in a big way.

"We've adapted to the situation fairly well," Cooper said. "We're highly supportive of one another, and we're a very enthusiastic group. We're going to get the job done."