Not something I devote a lot of thought to :). But really, there's always that slim chance the ball deflects the wrong way and it works out for the offense. It's not a 100% sure thing for the defense, that's why teams do it. Defenders still need to play it right. I don't really care how they get it done -- but there's no magic to it. As a defender, they still need to play good football, get in good position, and play the ball correctly. Bat it down, intercept it, however it happens, the defense still needs to "win" the play.