Thompson was hurt with 2 minutes, 22 seconds left in the third quarter after he went up for a breakaway dunk and was fouled by Toronto Raptors guard Danny Green with Golden State leading 83-80. Thompson came down hard and immediately grabbed the knee while writhing on the floor in pain.
The Warriors ruled Thompson out for the rest of the game, and he left the building on crutches, much the same way Kevin Durant did after rupturing an Achilles tendon in Game 5.
Thompson left the game in the midst of another great performance in the Finals. He had 30 points in 32 minutes, going 8-for-12 from the field and pulling down five rebounds. But it wasn't enough -- the Raptors won 114-110 to finish off a 4-2 series victory and capture their first NBA championship.
Asked what went through his head when Thompson went down, Warriors coach Steve Kerr said, "It's amazement that we're sitting in this position with -- during the game, we have a chance to win the game and force a Game 7, go back to Toronto -- you just think, 'How? How has this group of guys put themselves in position to do it?' And then, as I said, when Klay goes down and is out for the game, it's just sort of a, 'You gotta be kidding me. This has to stop.'
"But it's just -- the way it's gone, I don't know if it's related to five straight seasons of playing 100-plus games and just all the wear and tear, but it's devastating."
After making it about halfway there, Thompson turned around and headed back to the floor to take his free throws. If another player had taken the free throws, Thompson wouldn't have been allowed to return to the game.
Thompson's re-emergence on the floor received a raucous standing ovation from the crowd inside sold-out Oracle Arena.
Thompson proceeded to knock down both free throws, giving Golden State an 85-80 lead as Warriors fans chanted "MVP! MVP!" The Warriors fouled on the ensuing possession to get him back to the locker room to be checked out by the team's medical staff.
"It's just tough in terms of a guy like Klay that left it all out there," Warriors guard Stephen Curry said. "He was playing amazing tonight. And to see a freak play like that where he lands awkwardly. I don't know the diagnosis yet, but you think about the person and the guy and how much he loves to play the game, and that's the only thoughts you have. It's really not about what it means in terms of playing basketball. It's just I'm more concerned about him as an individual."
Thursday night's scene was eerily reminiscent of the one surrounding Durant's injury.
Warriors general manager Bob Myers and Warriors director of sports medicine and performance Rick Celebrini walked behind Thompson as he made his way back to the locker room, much like they did with Durant on Monday night.
Thompson suffered a left hamstring injury in Game 2 of the series and was forced to miss Game 3, despite pushing to play. He returned and was a stalwart for the beleaguered Warriors group throughout the series.
"Obviously he's a warrior," Warriors center DeMarcus Cousins said. "He's a true definition of a warrior. Dude [was] basically on one leg, and he's still trying to come out to play. To have a teammate like that, that's all you can ever ask for. Love that dude to death. I'd go to battle with him any night."