The Bears won't say how severe the concussion is. Cutler hasn't spoken to the media this week.
Campbell will be making his first start with the Bears. He has made 70 starts in his NFL career previously with the Redskins and the Raiders.
Campbell says he's been spending a lot of time this week watching film and preparing himself mentally. He says come Monday he'll just be himself on the field.
"You can't worry about doing things to please everyone. You've just got to try to play your game, because everyone knows you haven't played in a while of course, you're not going to be up here like Peyton Manning or anything," said Campbell Friday. "You've just got to do what you do."