When Max Kellerman says that Tom Brady will be "average at best", Stephen A. Smith argues that he is special and explains why the odds are in his favor to continue to be elite in the next couple years. (1:49)

New England Patriots quarterback Tom Brady has been lighting up the NFL since returning from his early-season suspension, emerging as a top MVP candidate despite missing four games.

The 39-year-old Brady ranks first overall in Total QBR, and has helped cast the Patriots in the role of most likely Super Bowl champion, at 32 percent according to ESPN's Football Power Index. That said, the data says New England should be thinking very long and hard about looking elsewhere to fill the starting QB role next season.

The Patriots, more than any other team, have made a habit of paying for likely future production and not past success. And though Brady's contract would make it difficult for them to merely part ways (more on that in a minute), at 39 years old they undoubtedly know what's coming for Brady.

Two of the most dominant quarterbacks of the past 20 years -- Brett Favre and Peyton Manning -- are, in fact, useful examples to project Brady's performance in the next few seasons. Favre, Manning and Kurt Warner join Brady in a rare group of players that even make it to this stage. Average quarterbacks rarely get a chance to continue to play past their mid-30s; once they show signs of decline, they're replaced. What remains are the Favres, Peytons and Warners (and even Warner stepped away at the age of 38) of the NFL, great quarterbacks who can continue to rely on their ability to run an offense and take advantage of defenses, even as their deep throws lose a little of their zip. But even the greats will eventually fall, as the numbers demonstrate.

Brady's performance at age 38 and up to his current age of 39.5 mirrors that of Manning at the same age. Brady has posted an average QBR of 70 during those years -- Manning's was 69. After age 39.5, however, Manning's performance declined sharply. For all of his games after the age of 39.5, he posted an average QBR of 49. The decline was part of a broader, ominous trend for Brady and older QBs.

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ESPN senior analytics specialist Brian Burke detailed this drop-off in a study for Advanced Football Analytics.

All QBs who played when they were 38 years old had QBRs above 70 in between 50 and 70 percent of their games. By age 40, their chance of posting a QBR above 70 drops to below 5 percent. This is the range Brady will be in at the start of the 2017 season.

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Availability becomes a major issue as well.

Again, looking at the group of QBs who were playing at the ages of 39 and 39.5, this group has a 71 percent chance of playing at least 10 more games. Once they get past 40 (where Brady will be when the 2017 season starts), that percentage drops by half. Only 35 percent who are playing past the age of 39.5 will play 10 or more games.

Given the Patriots' history of shedding iconic players (Lawyer Milloy, Logan Mankins, Randy Moss and Richard Seymour, to name a few), it shouldn't be a surprise if Brady is next on the chopping block, though his contract could give New England some pause. The Patriots tend to release or trade players at or near the end of their contracts so there is minimal, if any, dead money on the salary cap. But remember that Brady signed a new contract during this past offseason that included a $28 million bonus. By NFL cap rules, if the Patriots cut Brady after this season, they would carry a cap charge of $27 million -- nearly twice the price tag for keeping him ($14 million).

That reality means, should Brady's performance decline as the data nearly guarantees it will, Patriots coach Bill Belichick could find himself in the difficult position of benching Brady for a younger arm. While Belichick has never been accused of being overly emotional about his roster decisions, there should be little doubt that the notion of benching Brady would be an especially delicate situation for the organization and its fan base.

Whatever they decide, there is no reason to believe that Brady has the ability to beat the overwhelming trend of aging QBs. Father Time, as they say, is undefeated.

Brady image by AP Photo/Lynne Sladky

For more from ESPN Analytics, visit the ESPN Analytics Index.