In the NFL of old, quarterbacks approaching 40 did not exist because they were out of the league long before that numerical benchmark was staring them in the face. But in today's NFL, in which quarterbacks are much more protected and rule changes favor passing offenses, signal-callers are extending their careers and, more importantly, their primes.

That brings us to New England Patriots quarterback Tom Brady. Brady has enjoyed a decade-plus of elite play, but history tells us that should end this season. ESPN's Andrew Healy took a look at the 10 best offenses of all time and noticed that five of them returned the same quarterback for Year 11. Peyton Manning, Dan Marino, Dan Fouts, Bart Starr and Steve Young all led their teams for 10-plus years to great results, but mostly regressed to average (or worse) the following season.

"At 38, Tom Brady will be older on opening night than each of those five great quarterbacks was at the end of his offense's best 10-year stretch," Healy wrote. "Other than Manning, those quarterbacks were either out of the league or shells of their former selves."

Will Brady suffer the same fate?

"For Brady and his elite colleagues of recent past, not only does 38 look like the new 33, but playing at a high level beyond 40 also looks tantalizingly possible. Take the six likely future Hall of Fame quarterbacks who are at least 33 years old now: Brady, Drew Brees, Brett Favre, Peyton Manning, Ben Roethlisberger and Kurt Warner. They've gotten better with age...

"The signs look particularly good for Brady. Quarterbacks of the past usually started to miss games due to injury as they entered their mid-30s. Those injuries foretold future games missed and decline in play. Brady has not missed a game in seven years, and with his quick release adding to his injury avoidance, the late-career health issues that now appear to be swallowing Manning show no signs of arriving in Foxborough anytime soon."