A year ago, as the New England Patriots got off to a slow start, many theorized that Tom Brady's run was about over and the 37-year-old should start looking at his exit strategy. Brady then took the Patriots on an amazing run and capped his season with a Super Bowl win, finishing fourth overall in Total QBR.
Brady has openly discussed playing past 40, but Father Time is undefeated. How likely is it for Brady to continue to perform at a high level given that he is now 38? Is Brady performing better than other quarterbacks who made it to this stage in their careers? What can the careers of George Blanda and Warren Moon tell us about Brady and his future?
Unfortunately, we don't have the data to calculate QBR for Blanda or Moon, but we do have enough information to get a peek into Brady. Using data from every game in NFL history that was started by a quarterback who was 36 or older, we can start to get an idea of where Brady is in his career. Given the historical nature of the data, and how the game has changed over time, the data was adjusted to account for the era the game was played in (teams throw more now than when Billy Kilmer and Earl Morrall were behind center), and the quarterbacks' performances were adjusted for whether they were at home.
Once the data was adjusted and all quarterbacks were put on an even playing field, we can look at how many touchdowns a 38-year-old quarterback can be expected to throw in a game, and how Brady compares to that. Then, looking at where Brady is now, the data can tell us how his performance can be expected to change during the next few years.
Based on this analysis, the average 36-year-old starting NFL quarterback can be expected to throw 1.3 touchdowns per game. As he gets older, those expectations begin to drop -- falling to less than one touchdown per game for the average 40-year-old starter. Brady, however, is basically a touchdown better than the average aging quarterback -- and reasonably can be expected to throw two touchdowns per game two years from now, when he is 40.
Brady right now is outperforming other quarterbacks who were playing when they were 38, such as Fran Tarkenton, Brett Favre and Kurt Warner. He is also on track to be outperforming the two 36-year-old QBs who were starters at the beginning of this season (Carson Palmer and Drew Brees). He is not the greatest 38-year-old of all time, however; that distinction belongs to Peyton Manning.
Overall, provided Brady stays healthy, the numbers say he is in good position to continue playing at a fairly high level past his 40th birthday.