Shell did not speculate on the severity of Gallery's injury nor did he have an estimate for his return.
''How that's going to be, I'm not sure,'' Gallery said. ''I have to wait for (trainer Rod Martin) to explain to me what's going on with that.''
Gallery wasn't the only Oakland player not practicing Wednesday. Punt returner Chris Carr also left practice and was seen walking slowly and limping noticeably through the players' parking lot before practice ended.
Cornerback Nnamdi Asomugha (foot sprain), defensive end Kevin Huntley (foot sprain) and linebacker Sam Williams (ankle) were all held out of practice as well. Huntley wore a protective boot on his left foot.
Quarterback Aaron Brooks had an MRI taken on his knee and the results were negative, meaning he'll be back behind center against Baltimore.
''Much better, much better,'' Brooks said Wednesday when asked about his condition. ''The last couple of hours of intense rehab got me back to the point where I can practice and see what I can do.''