Three weeks into the NFL season and wide receiver Antonio Brown's release from the New England Patriots after an 11-day stint isn't even the most dramatic change in professional football. The quarterback carousel has been spinning with the Indianapolis Colts' Andrew Luck retiring, the Pittsburgh Steelers' Ben Roethlisberger out for the season due to injury, and the New Orleans Saints' Drew Brees, the Jacksonville Jaguars' Nick Foles, and the Carolina Panthers' Cam Newton all set to miss a significant amount of time.

Not even the Colts' legendary placekicker, 46-year-old Adam Vinatieri, looks immortal. The biggest change, however, may be yet to come.

At the conclusion of this season, 42-year-old Patriots quarterback Tom Brady becomes a free agent. It could be temporary; it could be a small bump on the road to another contract extension. But with Brady allowed to test the free agent market for the first time in his 20-year career, there is at least a small chance it could mark the end of an era.

Together Brady and Patriots head coach Bill Belichick have won six Super Bowl titles and nine AFC Championships. They have missed the playoffs only once and never posted a losing season with Brady as the starter. But their interests may finally be starting to diverge. Brady and Belichick have reached the point where the main argument their detractors use against them is each other.

Brady, unlike Peyton Manning or Joe Montana, his main rivals for the title of greatest quarterback of all time, has only played under one coach — Belichick. The "system quarterback" smear of Brady derives all of its superficial plausibility from this fact and the modicum of success Belichick has enjoyed with Brady backups.

Belichick's detractors nevertheless make a similar argument. They point out he has won exactly one career playoff game as a head coach with a quarterback other than Brady. He missed the playoffs entirely without Brady in 2008 and posted his only losing record with the Patriots in 2000, the season before Brady became the starter. Brady has also made up for some of Belichick's riskier personnel moves, such as ... signing Antonio Brown.

One way to swat down these arguments is for one or both of them to win without the other. Their partnership has been long and fruitful, but don't think for a moment that this hasn't crossed their minds. They are both team players, but they have their egos too. Seth Wickersham's memorable 2018 ESPN piece about a looming rift in the Patriots dynasty contained plenty of quotes critical of Brady that sounded like they came from Belichick-friendly sources.

The two may also be at odds over how their professional football careers end. "At some point, I want to create something that is truly great, and the measure of true greatness is something that lasts," Belichick was quoted as saying earlier this year. "It's not just winning a championship. It's something that lasts and lives beyond you." He invoked legendary San Francisco 49ers coach Joe Walsh as an example of the legacy he was trying to build. He's also repeatedly said it is better to part with a player a year too early than a year too late. He has already watched Brady's most promising understudy, Jimmy Garoppolo, leave and may not be eager to see current backup Jarrett Stidham follow him out the door.

By contrast, Brady has repeatedly said he would like to play football until he is at least 45. The "TB12" regimen and documentaries like "Tom vs. Time," both with an emphasis on longevity, are likely to be the focus of his post-playing career. This means it is in his interest to play as long as he can perform at a high level and try to at least get as close to 45 as possible, not hand over the reins to someone who can keep the Patriots winning once he's finally gone.

The construction of this year's Patriots team, from the number of veterans who were retained at the expense of younger talent to the short-lived acquisition of the extremely talented Brown in mid-downward spiral, has the feel of getting the band back together for one more tour. Or at least one more Super Bowl push.

Winning could keep Brady and Belichick together despite it all, of course. And the Patriots' ownership desperately wants Brady to retire a Patriot. A far more sentimental man than Belichick, Robert Kraft could easily intervene to prevent his star quarterback from ever donning another uniform.

Nothing is certain, but stranger things have happened.

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