It's this: Durant is currently the most powerful person in the NBA.
Ever since Shaquille O'Neal rocked the league by going to the Los Angeles Lakers in 1996, superstar free agency has been the NBA's most potent force. LeBron James' move to the Miami Heat in 2010 supercharged it.
Through an era that is defined by annual superstar movement, no single player has held the balance of power in his hands the way Durant seemingly does as he approaches next summer's free agency. He is a two-time reigning Finals MVP who wouldn't just completely alter the fortunes of a new team but also could derail one of the great dynasties in the history of the league in the same swipe.
Kobe Bryant's free agency in 2004 is one possible parallel, but even that one is flawed. At that point, the Lakers hadn't won a title in two years, and there weren't a handful of teams out there in desirable cities with wide-open salary-cap space to welcome him, as Durant will have in July 2019.
The only true threat to lure Bryant was the then-hapless LA Clippers, and that saber-rattling was enough to get owner Jerry Buss to trade O'Neal when he still had years left in his prime. That was some pretty impressive might from Mr. Bryant, and it still wasn't at the level of what is unfolding now.
Durant could be looking over his shoulder at a three-peat in Golden State with a couple of in-their-prime future Hall of Famers, probably the most incredible arena in the world ready to open and a legion of Silicon Valley execs lining up to give him first looks at Series A funding.
The ability to say no to that is as powerful as it gets in the American sports landscape. It's unprecedented.
This reality is discomforting within the Warriors. You think Green hadn't been contemplating it long before his rant spilled out in fury earlier this week? You think owner Joe Lacob's joking about Durant signing when he handed him his ring on opening night isn't based in some genuine concern? You think James' checking in with Durant about whether he'd want to sign with the Lakers this past summer was only a throwaway flier?
Everyone in the league knows Durant might leave next summer. Just as everyone in the league knew James might leave Cleveland a year ago. The difference was that he wasn't going to be walking away from a team defending multiple titles. Everyone knew that, too.
But Durant, like James, has shown the guile to walk away before. You may dismiss the concept of Durant walking as impossible because no one has walked away from a three-peat (although Jordan did, twice, with his retirements). But you'd underestimate what it took for Durant to turn his back on Oklahoma City. If he can do that, he can do anything.
Maybe not, though, right? Maybe Durant re-signs for five years and $200 million-plus on July 1. Maybe the Warriors have a magical run and win three more titles in the next four years like they just won three in the past four. Maybe Durant or Green ends up as the best man at one or the other's wedding. In the NBA, making assumptions, especially about free agency, is often foolish.
But that's not the point. The point is at this place in history Durant has more control over the future of the league than any player we've ever seen. More than any owner, player or commissioner.
That, right there, is the definition of power.