The Browns placed inside linebacker D'Qwell Jackson on injured reserve Tuesday, ending Jackson's season.
Jackson suffered a shoulder injury late in the second quarter of Sunday's 27-14 loss at Pittsburgh and did not play in the second half.
''It's disappointing any time you lose a player for the season, and this is especially true with someone like D'Qwell, who has proven to be an outstanding leader for us both on and off the field,'' Browns coach Eric Mangini said in a statement.
A second-round draft choice in 2006 out of Maryland, Jackson ranks third in the league in tackles with 59, in statistics on NFL.com. Browns statistics credit him with 57 tackles, two passes defensed and a forced fumble.
Jackson led the Browns in tackles in 2008 and 2007 and finished second as a rookie. He was also elected a co-captain this season.
Kaluka Maiava, a fourth-round pick from USC, replaced Jackson against the Steelers, but struggled in pass coverage. Jackson's absence could also mean more playing time for David Veikune, a second-round pick from Hawaii.
The Browns also made adjustments with defensive linemen on their practice squad, signing Keith Grennan and releasing Carlton Powell. Grennan had been on that squad until Oct. 9.