The Thunder has owned the best record in the Western Conference every day this season.
OKC won on opening day, went 5-0 the first week and has never looked back.
But with San Antonio's 114-105 victory over the Thunder on Friday night, images in OKC's rearview mirror suddenly are closer than they appear.
The Thunder (33-11) still leads the Spurs (29-13) by two games in the loss column, but it would have been by twice that many had OKC been able to complete an unfathomable comeback before another sellout crowd of 18,203 at Chesapeake Energy Arena.
Down 27 points in the second quarter, the Thunder slowly clawed back, began a 14-0 run at the end of the third quarter and pulled to within two points on two occasions midway through the fourth quarter.
That's when the Spurs, who have been making clutch plays for more than a decade under coach Gregg Popovich, regained control with suffocating defense and patient offensive execution at key moments.
"We should never get down 27 points, unfortunately we did," OKC coach Scott Brooks said.
Now the Western mountaintop where the Thunder once had solid footing has become a slippery slope. OKC is 4-4 over its last eight games and its next 11 games are against teams still in the playoff hunt.
Once 17-1 at The Peake where it had won 14 straight, the Thunder is now 18-4 at home where it has lost three of its last four.
Meanwhile, San Antonio remains the NBA's Rock of Gibraltar, somehow winning roughly 70 percent of its games despite being without one of its best players in Manu Ginobili, who has missed 28 of 42 games, including Friday night against the Thunder.
"We had a great night," Popovich said afterward. "Oklahoma City had a tough start. They missed some easy shots inside and couldn't get a jumper to fall so we were able to get a lead."
Before the game, Popovich couldn't come up with an answer on how to slow down the Thunder.
"One does not slow them down much, I don't think," Popovich said. "They're going to run. They're talented, deep, well-coached. It's a helluva team and it's become a great organization. Whenever anybody plays Oak City, it's a challenge for them because so many good things at both ends of the court."
Turns out OKC slowed itself down, shooting just 30.4 percent (7 for 23) from the field in the first quarter, and that's with James Harden converting a 3-pointer at the buzzer.
The Thunder's shooting improved slightly each quarter thereafter, but it wasn't enough to overcome the team that's gaining in the rearview mirror.