The only problem was that the Bears also took away Graham in the first half. He didn't have any catches until right before halftime. But, Brees has so many receivers (usually has multiple completions to more than 5 receivers per game) that he can usually just pick someone else until you start focusing on them. Usually, it gets to the point where Brees/Peyton will hurt you with the other weapons, and you have to defocus on Graham.
For some reason, that just didn't happen.