The team placed Brown on injured reserve Thursday after he missed Wednesday's practice. Terrence Metcalf will take Brown's place in the starting lineup Sunday against the Oakland Raiders.
"Ruben has been practicing once a week for the most part, and he's been dealing with some pain," coach Lovie Smith said. "He wasn't able to finish the last football game, but you know, you play with pain always. You don't know the extent until you get to that point where you're told it's not getting better. He needs to get it fixed."
Brown was not available for comment. The injury is another blow to a Bears offense which has struggled with a league-high 16 interceptions and ranks next-to-last in rushing at 78.9 yards per game.
Brown's ability to play in pain had earned him respect from teammates.
"He couldn't even use his arm most of the times in the fourth quarter but he was just going anyway," center Olin Kreutz said.
Brown signed a one-year contract before the season. Whether he returns for another year or retires is uncertain.
"We'll miss him a lot," Smith said. "Hopefully he can get the shoulder taken care of and come back stronger than ever."
Metcalf is a 6-foot-4, 318-pound, six-year veteran from Mississippi who has started 20 games.
"I've been here for six years and we've been in this offense for three years now," Metcalf said. "I know the offense. I'm just going out and do the job that they hired me to do."
Only five of Metcalf's 20 starts came at left guard.
"With our offensive line staying intact for the most part, he hasn't gotten a lot of playing time," Smith said. "He's one of the guys. It should be a pretty easy transition with him moving in. Again, the players know him, he knows the system, and what were trying to do. Hopefully, we can get the same good play from that position."
Guard-center Anthony Oakley was promoted from the practice squad to fill Brown's roster spot.
Smith also said cornerback Nate Vasher, who hasn't played since Sept. 23 and who missed practice again Thursday, was unlikely to play in Sunday's game. Vasher said he still has not run full speed or backpedaled in rehab from a partially torn groin muscle.
"When you're dealing with a muscle, it's hard to know exactly when you'll get over the hump completely," Smith said.
The Bears also placed running back P.J. Pope on the practice squad injured list and signed defensive end Chris Frome to the practice squad.
Copyright 2007 by The Associated Press