Tom Brady stats, total vs. 4th quarter:
2012
Tot: 65.8%, 7.6 ypa, 97.2 rating
4th: 58.6%, 7.7 ypa, 93.2 rating
2011
Tot: 65.6%, 8.6 ypa, 105.6 rating
4th: 66.4%, 8.6 ypa, 107.1 rating
2010
Tot: 65.9%, 7.9 ypa, 111.0 rating
4th: 64.9%, 7.6 ypa, 106.7 rating
2009
Tot: 65.7%, 7.8 ypa, 96.2 rating
4th: 60.3%, 5.7 ypa, 75.9 rating
2007
Tot: 68.9%, 8.3 ypa, 117.2 rating
4th: 65.0%, 8.9 ypa, 114.4 rating
2006
Tot: 61.8%, 6.8 ypa, 87.9 rating
4th: 61.7%, 6.3 ypa, 85.0 rating
2005
Tot: 63.0%, 7.8 ypa, 92.3 rating
4th: 63.6%, 8.0 ypa, 91.3 rating
2004
Tot: 60.8%, 8.0 ypa, 92.6 rating
4th: 54.9%, 7.3 ypa, 72.3 rating
2003
Tot: 60.2%, 6.9 ypa, 85.9 rating
4th: 60.4%, 6.1 ypa, 85.8 rating
2002
Tot: 62.1%, 6.3 ypa, 85.7 rating
4th: 58.0%, 6.6 ypa, 91.6 rating
2001
Tot: 63.9%, 6.9 ypa, 86.5 rating
4th: 58.2%, 5.9 ypa, 75.1 rating
What does this tell us? It tells us that pretty consistently over the course of his career, Tom Brady has been a less effective passer in the 4th quarter than he has been in the rest of the game. Keep in mind that the "Tot" stats above *include* the 4th quarter numbers, which tend to pull the totals down. So the disparity between quarters 1-3 and quarter 4 is actually bigger than these numbers suggest.
Bottom line: Tom Brady is a great, great quarterback, who has a ton of comeback wins and clutch performances. But over the course of his career, even in the years when they won the Super Bowl, he's been a worse QB in the 4th quarter. Those are the facts.