Drewwho almost had it - it wasn't pressure of the game though it was cumulative pressure of the season. Mental and physical. It had nothing to do with the streak. He has dealt with that mental pressure before, but the added responsibility he has assumed as a team leader as well as the leader of the offense, the increased physical abuse he took this season, the added pressure of compensating for a porus defense for the first 10 weeks of the season, and his utter frustration with an inconsistent offense that he just couldn't just fix by elevating his own game, seemed to really drag him down.
Brady's no dope. I think he knew that for some reason he was on an island this season more than ever before and try as he might he couldn't will his weapons to follow him. He was right. Guys were slow out of the blocks (perhaps some basked a tad too long in the glow of their second SB victory in two seasons), others were plagued by injuries, and they never got a chance to establish much rapore or consistency throughout the season. Remember, he was again throwing and handing off to street FA but not for just a game. The revolving door that was his supporting cast was legion. Once the defense started to gel they were solid. The offense performed in fits and starts but they never really gelled or got consistent.
The good news is I think BB recognizes all this and will do things to remedy some of the problems. I also think much like after 2002 we have a team that has tasted both victory and defeat and cannot tolerate the latter. They also have about a month more to rest up and will have fewer distractions to deal with in this offseason. Listening to Colvin this AM (and he's usually a pretty laid back guy) the angry desire to get back on the field and right the universe is palpable!