The 49ers' defense will be facing quarterback Jason Campbell when the Chicago Bears visit Candlestick Park on Monday night, as Jay Cutler has been ruled out because of a concussion.
Alex Smith is also coming off a Sunday concussion but he is on track to start for the 49ers, having practiced in a non-contact capacity Wednesday and Thursday.
The Bears ruled out Cutler before Friday's practice. He did not participate in Thursday's session. Campbell will be backed up by the recently re-signed Josh McCown, who played for the 49ers in the 2011 exhibition season.
Campbell was 11 of 19 for 94 yards in relief of Cutler on Sunday, when the Bears suffered only their second loss in nine games, a 13-6 home defeat against the Houston Texans.