Monday Night Football will be a battle of the backups pitting Jason Campbell and the Chicago Bears versus Colin Kaepernick and the San Francisco 49ers. That's because both starters have been ruled out due to concussions. Alex Smith of the 49ers was not cleared by an independent neurologist, Chris Mortensen of ESPN reported, and can't play based on the NFL's concussion protocol. The Bears ruled their own quarterback, Jay Cutler, out because of concussion symptoms. Cutler was concussed when he was hit in the helmet by Texans linebacker Tim Dobbins last Sunday night. Campbell replaced Cutler behind center to start the third quarter. Kaepernick played the entire second half and overtime in Smith's stead, completing 11 of 17 passes for 117 yards and rushing for 66 yards and a touchdown.