The Oklahoma City Thunder were riding high. They led the Golden State Warriors, the best team in regular-season N.B.A. history, three games to one, and were on the cusp of a huge upset and a trip to the finals.
Then it all started to go wrong.
But they still had the one-two punch of Durant and Russell Westbrook.
On Monday, in the most momentous decision in the N.B.A. since LeBron James’s “Decision” in 2010, Durant decided to leave town to join the rival Warriors.
In a flash, the Thunder went from contenders to also-rans. Oddsmakers hustled to change their lines, and around Las Vegas, the Thunder, previously 6-1 or so, can now be bet at 25-1 or more to win the title. Even at that price, you imagine that there will be few takers.
In losing Durant and Ibaka, the Thunder will be without 33 percent of their scoring, 28 percent of their rebounds and 48 percent of their blocks next season. They will also miss the face of the franchise, Durant, who had been with the Thunder since the 2007-08 season, when he was 19 and the team was still the Seattle SuperSonics.
When James left the Cavaliers, they tumbled from 61 wins to 19 in a single season. The Thunder are in better shape than the Cavs because they still have their star point guard, Westbrook, and his 23 points and 10 assists per game. He will have the promising young big men Steven Adams and Enes Kanter as teammates, and Victor Oladipo, acquired in the Ibaka trade, is a solid backcourt mate. But it is hard to see the Durant-less Thunder performing at the high level they did last season.
There is precedent for Westbrook playing without Durant. In the 2014-15 season, Durant played only 27 games. Westbrook responded by leading the league in field-goal attempts and winning the scoring title, both for the only time in his career.
Worryingly for the Thunder, Westbrook can leave next year as an unrestricted free agent. With the team very likely tumbling down the standings, why would he stay?
Another difference with Cleveland is the reaction of management to the star’s departure. The Cavaliers owner Dan Gilbert responded to James’s exit with an angry screed that included phrases like “cowardly betrayal,” “shameful display of selfishness” and “heartless and callous action,” published bizarrely in the silly-looking Comic Sans font.
In contrast, General Manager Sam Presti of the Thunder was disappointed but gracious about Durant’s departure. “He called me with his agent and business manager, and we had a conversation; Kevin was great,” Presti said.
In a statement, he said, “Kevin made an indelible mark on the Thunder organization and the state of Oklahoma as a founding father of this franchise.”’
Understandably, there has not been the same equanimity from fans, and jersey burnings were reported. Many neutral N.B.A. fans have awarded the title to the Warriors presumptively and complained that next season has been ruined for them.
The Thunder certainly have salary cap space now, and will have even more if Westbrook leaves. But they also have the difficulty of attracting stars to unglamorous Oklahoma City. There are already calls from some to trade Westbrook now and rebuild the team from scratch. If they do, the post-James Cavs’ 19-win total may be threatened.
Commissioner Adam Silver has said that the distinction between cities in the N.B.A. is no longer as important as it was. He reasons that the equally shared television revenue puts all teams, regardless of their locations, on an even playing field, more or less.
But an Oklahoma City Thunder without Durant and Ibaka, and maybe soon without Westbrook, starts to look like a very small-market team indeed.