There's a fairly largely spread notion that Tom Brady benefits from his defense and that he has over his entire career- and this idea is followed by a postulation that the defense has inflated Brady's value throughout his tenure in New England.
It's absolutely true that the Patriots defenses have helped with the franchise's success over the past fifteen years, but to use that as a way to lessen Brady's impact with the offense appears to be disingenuous.
Football Perspective's Chase Stuart decided to run the numbers of every quarterback since 1960 to see what their record was in games where their defense allowed 21 or more points. In 106 games, Brady has a record of 60-46, or .566. According to his expectations, Brady has 33.5 more wins that would be expected of any quarterback with 106 games.
This is the most wins above expectation of any quarterback in his data set. The Patriots offense wins more games than any other when the defense comes up short, and we all know how much offensive success is linked to quarterback prowess (answer: a lot).
Out of quarterbacks with 20+ appearances, Brady has the best winning percentage as one of four quarterbacks with a .500 or better winning rate (Otto Graham, 0.548; Daryle Lamonica, 0.543; Joe Montana, 0.500). According to Stuart's data, teams win roughly 25% of the time when their defense allows 21+ points, and Brady's Patriots win over twice as frequently.
If we compare with contemporaries, Aaron Rodgers ranks 5th all time (0.472), Peyton Manning ranks 8th (0.439), Andrew Luck ranks 10th (0.414), and Tony Romo ranks 12th (0.403). No one else wins 40% of their situations.
Again, it's important to reiterate that offensive production is not purely on the shoulders of the quarterback, but it's no coincidence that the top five active quarterbacks are considered to be the best in the league. And no one is better than Brady.