The extra week of preparation might give Belichick’s Patriots an edge. So, undoubtedly, will the unique character of the Patriots’ defense. Theirs is the only unit in the league that switches back and forth from a 3-4 to a 4-3, defying characterization and confusing opponents. "That gives you fits," Bills coach Gregg Williams says. "It adds practice time and game-plan time. And to their credit, they are flexible enough personnel-wise to do it."