When did you know that Kevin Durant was leaving? Was it when The Undefeated reported that Durant was 90 percent sure he would stay in Oklahoma, and would need to hear “an amazing sales pitch” to change his mind? Was it when you heard that he would be hearing those sales pitches in the Hamptons? That he was “blown away” by the Clippers presentation? That Boston was bringing Tom Brady, and had just agreed to terms with Al Horford? Was it on Sunday afternoon, when NBA gambler-pundit Haralabob Voulgaris cryptically tweeted this?

I knew when Tim Kawakami reported that Durant had spent time on the phone with Jerry West on Saturday. This was a day after he had met with the Warriors’ traveling band of Steve Kerr, majority owner Joe Lacob, GM Bob Myers, Steph Curry, Klay Thompson, Draymond Green, and Andre Iguodala. And I was certain when I read that the Oklahoma City cohort making the final pitch to Durant on Long Island included Thunder chairman Clay Bennett.

No shots at Bennett (I will leave that to you, Seattle), but his presence highlighted the differences between those pitching Durant on leaving and the team trying to get him to stay. Boston, Miami, the Clippers, San Antonio, the Warriors — they variously had NBA titles, history, team legends, stars from other sports, bigger media markets, and more cosmopolitan locations to offer. The Thunder ultimately had one thing to sell to Kevin Durant: Kevin Durant.

Shortly after Durant announced his decision to leave Oklahoma City on The Players’ Tribune today, the Thunder released a statement. In his remarks, general manager Sam Presti called Durant “a founding father of this franchise.”

This statement is true, and remarkable. There were no Thunder before Durant. To a lot of people, even outside of Seattle, this was a franchise born of theft. Durant has done a lot of amazing things during his time in Oklahoma City, but making and keeping this team likable was perhaps his greatest achievement. Along with Russell Westbrook, Durant made Oklahoma City into a viable and successful NBA organization, despite some of the organization’s self-sabotaging moves.

And it’s hard to imagine what the franchise will be without him.

Westbrook is better than anyone could have hoped, but Durant is what we all expected. We knew that as long as he was healthy — and there were some dark days on that front — he was going to be one of the greats. You could gamble on losing James Harden because you had Durant. You could fire a coach and hire one out of the NCAA because Durant would make it easy for him. A healthy Durant and Westbrook guaranteed postseason basketball, sell-out crowds at Chesapeake Energy Arena, gawking fans on the road, and jerseys in the top 10 of sales. Kids who ordinarily couldn’t find Oklahoma City on a map rocked T-shirts with the team’s name on it. As Durant went, so went the city, and the franchise.

And now he’s gone. For the local fans of the Thunder, this probably feels like a death in the family. To lose your best player to your biggest rival is about as bad as it gets. Like LeBron in Cleveland, Durant was the team. He pumped life into the organization. Without him, the team is in free fall. We’ve been living through these “decisions” for six years now, and while they never fail to entertain, they seem to be getting more theatrically cruel to the team that loses the deciding player.

And the white-knuckle days are just beginning in Oklahoma City. Russell Westbrook is an unrestricted free agent after next season. We’ll have to wait for him to give some sort of statement about Durant leaving to gauge how he’s feeling about this, but for any player — even one capable of going Wolverine berserker like Russ — the mission to win a title in Oklahoma City, with Golden State in the same conference, becomes a nearly impossible one. Some think this will only strengthen Westbrook’s resolve to stay, but I’m not so sure.

Westbrook might not be the one deciding his own fate, anyway. This is Presti we’re talking about. I’m sure his hair moved a little when he got word that Durant was leaving, but he will have been ready for the possibility.

According to ESPN’s Brian Windhorst, if Westbrook turns down a new deal with the team, there is some belief around the league that Oklahoma City will look into dealing its last star player. The Serge Ibaka trade looks a lot like doomsday prepping now, doesn’t it? Presti acquired a good, young, two-way player in Victor Oladipo to pair with Russ, along with Domantas Sabonis (the 11th pick in this year’s draft) and Ersan Ilyasova. When the trade happened on draft night, it felt like the Thunder were getting younger and deeper, saddling up for another run at the Warriors. Now it looks like they were collecting talent for a post-KD future.

They can radically change that future by dealing Westbrook. The Trade Machine will be humming with folks plugging in pieces from the Lakers, Sixers, Celtics, and more. Nobody in Oklahoma City wants to hear this, but the craziness is just beginning.

Unless Presti absolutely fleeces some team, Oladipo turns into a 25-points-per-game scorer, or Steven Adams keeps getting better, the Thunder will regress. With Westbrook, it’s not hard to see them in the Utah and Phoenix tier of Western Conference teams.

The worst possible outcome would be Westbrook leaving and the Thunder getting nothing in return. I’m sure Presti is kicking himself for not getting any return on Durant’s exit. Durant agreed to a two-year deal, with a player option in the second year, so there will be no compensation for his departure. Presti cannot let that happen with Westbrook. If they have Westbrook, the Thunder won’t be a lottery team, so they will miss out on the Lonzo Ball, Harry Giles, and Josh Jackson sweepstakes. If he were to leave in free agency, they could be looking at a completely bare cupboard in 2017–18. It is not an overstatement to say that that could spell the end of the franchise in Oklahoma City.

Will we look back on the last eight years of the Thunder as a complete fluke? Did they just get supremely lucky in the draft — selecting Durant, Westbrook, Harden, Ibaka, and Adams — only to see them leave or get traded away, one by one? Will fans still come to games at the 18,000-seat Chesapeake Energy Arena to watch Oladipo and Cam Payne? Forget the history of the team. The founding father just left the building. Now the future is in jeopardy.

I will back away slowly and let Oklahoma City fans ponder that. For them, this is deeply personal. But there are Oklahoma City fans, and then there are Thunder fans. Thunder fandom extended beyond Oklahoma City lines. For some people, myself included, the “Thunder” was an idea. It was watching these two kids grow up together:

It was watching them persevere through bad trades, uninspired coaching, and terrible injury luck. It was watching in wonder as dead weight like Dion Waiters, Thabo Sefolosha, Andre Roberson, D.J. Augustin, and the ghosts of Derek Fisher and Kendrick Perkins rose with their tide but also kept them from reaching their greatest possible heights.

Only “Thunder” fans are going to pick up on this frequency, but the friction between Russ and Kevin was kind of the whole point. The anxiety produced its own narcotic high. It produced a misguided, deluded, ecstatic confidence. It allowed us to see the Thunder down by four to the Clippers, with 40 seconds left in a playoff game, and feel like, you know what, they got this.

Westbrook and Durant was like watching two guys perform a Coast Guard helicopter rescue in the Atlantic in stormy weather. Holy shit, ARE THEY GONNA PULL THIS OUT OF THE WAVES? IS THE CHOPPER GOING DOWN? OH MY GOD, THE CHOPPER DUNKED A BASKETBALL.

That was this postseason. That was watching them roast the Spurs and then the Warriors in their own buildings. That was the Thunder turning into a long-limbed defensive octopus, cutting off all of Steph Curry’s passing lanes, and running all over the Warriors. Then came Game 6 of the Western Conference finals — what we now know was Durant’s last game as a Thunder player in Oklahoma City. That’s all over now.

Most NBA teams are not free-agent destinations. The Thunder were a beacon signalling that you could get insanely lucky in the draft and build something to last a generation. They could have been the Spurs. Now they’ll be the Jazz if they’re lucky.

Cheering for the Thunder was like cheering for a college team where the players stayed for eight years. Intellectually, you know that’s not fair to the players, no more than it is fair to the kids in school who waste prime wage-earning years not being compensated. But emotionally, a bond forms between the players and the fans. Watching a group grow up, and try, over and over again builds up anticipation. In Oklahoma City, that anticipation is gone. Now there’s only dread.