I think Brady made another mistake that 2007 Superbowl, and it goes to an ankle/foot injury. He was seen a week before the game down in New York with a boot on his foot - giving away that he had an injury, and the Giants D took advantage. I remember just being pissed that he was in NYC dancing or whatever when he should have been home studying film or whatever. Don't think he makes those kind of mistakes these days - he's all business.
I also attribute a mistake by Brady to the other Giants loss - and that's the safety to start the game (which in a sense spotted the Giants 9 points to start the game, as the D that held the G-men to 3 and out then had to unexpectedly come back out).
But what I really wanted to mention was Belichick's underrated D, which I was introduced to in 1994 in Bledsoe's first playoff game when the Browns (coached by BB) beat us in an ugly game. I just remember how frustrated I got in that we couldn't do anything. He did it again in 1999 when he was DC of the Jets and started our second half slide (after going 6-2) that led to an ignominius 8-8 ending and the sack for Pete Carroll. Every defense after that played Bledsoe the same way until he finally left the league.
Belichick is good, and he analyses you and takes away things you take for granted. Not sure if Atlanta has played against someone like him, but he can be very frustrating for an opposing offense, who often after the loss insist they were still the best team.
So they dismiss Belichick and that defense at their peril.