BEREA, OHIO (AP) - There's another new, gaping hole in the middle of the Browns' defense.
They may actually be able to plug it this time.
Starting inside linebacker D'Qwell Jackson will be sidelined for a few weeks _ and possibly longer _ with an injured right pectoral muscle, the second chest muscle injury the dependable four-year veteran has sustained in less than a year.
Browns coach Eric Mangini said Thursday the team will let Jackson's injury "quiet down" for several weeks. He will begin rehab and be re-evaluated.
At this point, there are no plans for surgery, but Jackson is getting a second opinion from Dr. Frank Cordasco, the New York-based surgeon who repaired his left chest muscle in October.
Agent Brian Mackler said he may have a update later on Jackson.
Jackson, who missed Cleveland's final 10 games last season when he tore the muscle away from the bone during a game against Pittsburgh and needed surgery, injured his right muscle during practice Tuesday. He left the field and was visibly upset when he returned to watch the final 30 minutes.
The temporary loss of Jackson will force the Browns to shuffle their linebacking corps, a unit the club strengthened during the off-season by signing free agent Scott Fujita, who won a Super Bowl ring with New Orleans, and acquiring Chris Gocong, a three-year with Philadelphia, in a trade.
Gocong has been playing alongside Jackson in the interior of Cleveland's 3-4 alignment during camp. With Jackson out, Eric Barton likely will slide into the middle, a spot he owned until injuring his neck and sitting out the Browns' final eight games last season.
Linebacker is the one position where the Browns can claim to have some depth. They're about to find out how dense it really is.
"This will be a test," Gocong said following the first of two practices Thursday as the Browns got ready for their exhibition opener Saturday in Green Bay. "We're definitely going to move guys around and see what fits where. We're going to have to move some guys around."
Along with Fujita, Gocong and Barton, the Browns could use David Bowens, Kaluka Maiava and Jason Trusnik in the middle.
"We've got a lot of guys who can do a lot of things," Trusnik said.
Mangini has a comfort level with Barton, who was leading the Browns in tackles when he got hurt last year. Mangini and Barton spent three years together in New York, and the coach trusts his knowledge in coordinator Rob Ryan's attacking system and ability to make the right calls.
Mangini knows nothing can replace hands-on experience.
"It's nice to have the guys that we have with the experience that we have here," Mangini said. "Eric Barton has started over 100 games through the course of his career, and Chris with his experience and David Bowens with this experience, Kaluka (Maiava) got some time last year as a young guy, right on down the line. I think it does help."
On paper, Cleveland's defense looks better than last year's group, which finished ranked 31st overall, 28th against the run. Ryan and Mangini are optimistic that his defense will be vastly improved, but they won't know for certain until the season kicks off.
Meanwhile, the Browns will miss more than Jackson's tackling. One of the team's most respected players, he impressed his teammates with a strong off-season of conditioning. Disappointed that the Browns would not sign him to a long-term contract, Jackson signed a one-year tender worth $1.76 million.
He was counting on big year to parlay into a big, free agent contract next winter. Now, he faces an uncertain future.
"He's not thinking negative about it," said safety Abram Elam, who spoke with Jackson on Wednesday. "He's trying to bring some positive into it. He's optimistic. Last year when we lost D'Qwell, we had to come together and it gave other guys opportunities. We have to do it again."
Notes: Punter Dave Zastudil has returned to Ohio after visiting his knee surgeon in Colorado. Mangini said there are no immediate plans for Zastudil to have surgery. He had a torn patellar tendon repaired in his right (plant) leg in December after missing eight games in 2009. ... Mangini plans to play QBs Jake Delhomme and Seneca Wallace one quarter each on Saturday. ... CB Brandon McDonald practiced after missing two days with a tender ankle. ... RT John St. Clair was carted off after cramping up during post-practice sprints in the swampy heat.