Linebacker depth was already a problem for the Eagles before Thursday night’s game in Pittsburgh.

It’s even worse now.

Seventh-round rookie Joe Walker suffered a season-ending ACL tear during a kickoff against the Steelers (see story), which leaves the Eagles without their promising young backup MIKE linebacker.

“Yeah, I think we’re going to continue to look at that obviously,” head coach Doug Pederson said on Saturday morning, when asked about the team’s need to bring in a veteran linebacker. “That’s been a spot that we’ve looked at all offseason and also in training camp. I know Howie (Roseman) and his team are out there looking.

“With the loss now to Joe, obviously, something’s gonna have to be done.”

That something could end up being 31-year-old free agent Stephen Tulloch, who has been long-linked to the Eagles because of his past with defensive coordinator Jim Schwartz.

For now, though, the backup middle linebacker is Don Cherry, an undrafted kid from Villanova who wasn’t signed until July 23. That means, unless the Eagles go out and sign someone, the Eagles are one Jordan Hicks injury away from Cherry.

“Joe’s a good friend of mine,” Cherry said. “I obviously didn't want this to happen, but I have to step up now, whether it’s special teams or defense.”

Veteran Eagle Najee Goode has experience playing in the middle, but has been Mychal Kendricks’ backup at the WILL linebacker spot. Kendricks was expected to return to practice Saturday, but missed the first two preseason games. Nigel Bradham is the starter at SAM.

Cherry spent some of the spring with the Bears, but was cut in June. He was on the street for a month before the Eagles signed him and plugged him in as the third-team middle linebacker.

“There’s definitely some pressure that comes with playing the MIKE,” Cherry said. “You obviously have to get the call, you have to learn all the signals, you have to get everybody set up. You have to keep everybody calm, you have to echo any of the adjustments you’re getting in the headset, whether it’s in practice or it’s in the game.

"You know, it’s definitely been a bigger task, where as if I came in playing the SAM or WILL it might have been easier to just worry about my job. But as the MIKE, I have to worry about everybody on the field. It’s definitely been a bigger adjustment.”

As for Walker, the rookie out of Oregon said he isn’t exactly sure how he hurt his knee, but it happened without contact.

Wearing a cumbersome brace on his left leg Saturday, Walker said the surgery hasn’t yet been scheduled.

“It’s difficult coming out here and trying to compete and having something like this happen,” Walker said, “but just trying to take the positive and keep moving forward.”

The Eagles, without Walker, will need to do the same.