Honestly, and this sounds crazy, but I really think that they've been holding back their blitz packages for this game. I think they feel they can get pressure with their front four guys, and for the most part (Jets game, blehk) they have. So if you're getting pressure with four, don't give bellichek anything to prepare for. I would be shocked if we only rush four against Brady since everyone knows the way to beat him is to knock him on his ass. And frankly, if we don't get pressure, I am not convinced that our corners can keep up vs Brady.
edit: I feel I worded this wrong. I don't think they were like we're not blitzing until we play New England, I just think they've only blitzed when they've had to to give opposing coaches the least chance to prepare.