Jackson is awaiting results of an MRI to determine severity of injury.
UPDATED: 10:50 p.m.
D'Qwell Jackson may have suffered another serious injury to his pectoral muscle during Tuesday's practice session.BEREA, Ohio -- Browns linebacker D'Qwell Jackson, who's been making a valiant comeback this season from a torn pectoral muscle, suffered an injury to the other pectoral Tuesday night in practice, a source told The Plain Dealer.
The extent of the injury is unknown, but Jackson looked upset and was being consoled by teammates during and after practice.
Jackson underwent an MRI Tuesday night. It could be anything from a sprain to a season-ending tear that could require more surgery.
Jackson, who had been starting all camp at inside linebacker, walked off the field midway through practice very slowly and with his head down and accompanied by a member of the training staff. He returned later in the session with a towel around his neck and looking upset.
One by one, players came up to express their concern. Voted a team captain last season, Jackson is one of the most well-liked players on the team. Close friends such as safety Mike Adams spent time talking to him, and he walked off the field with defensive coordinator Rob Ryan.
Until the injury, it had been an encouraging camp for Jackson, who worked tirelessly in the off-season to recover from October surgery. He's been in the starting lineup since day one camp, playing mostly alongside Chris Gocong, but with Eric Barton being worked in more as he recovers from neck surgery.
Barton and Kaluka Maiava worked a lot with the first team after Jackson left the field Tuesday night. Jackson's camp came after a tumultuous off-season in which he didn't receive the long-term deal he said the previous regime promised. But a trip to Africa to work with the impoverished had him feeling grateful just to be out on the field again.
Coach Eric Mangini said last week that he was pleased with Jackson's progress. Jackson led the NFL with 188 tackles in 2008.