Novak Djokovic crashed out of the second round of the Paris Masters, while Andy Murray, Juan Martin Del Potro and David Ferrer advanced into the next round.
Djokovic made a grand entrance onto the court, wearing a Darth Vader mask in tune with Halloween, but the match against American Sam Querrey turned out to be a nightmare for the Serbian.
Djokovic looked in complete control of the match, taking the first set 6-0 in just 20 minutes, but Querrey found form in the middle part of the second set, before forcing a tie breaker which he won 7-5. The final set also went the American's way, taking it 6-4, and with it one of the biggest wins of his career.
"I was concerned about how long I can keep that level, since physically I'm not feeling very good in last couple of days," Djokovic said. "When you're playing somebody that hits, that serves that well in the corners, there is nothing you can do.
"During the second set I already felt that physically I'm down, and I struggled every game.
"It's unfortunate, but on the brighter side, I have a little bit more time to rest because I had really difficult period in the last couple of weeks. Some things happened and (there are) a lot of things on my mind."
Querrey will now face Canadian Milos Raonic in the next round, after the youngster defeated Jeremy Chardy 6-7 (4), 7-6 (4), 6-3.
Murray had no hiccups in his second round match, defeating wildcard Paul-Henri Mathieu 7-5, 6-3. "I served well," the Scot said. "I didn't start the match off returning particularly well.
"I was struggling a bit with the timing on that. I think towards the end of the first set, we started to have a few more rallies. But the conditions were fast."
Argetnine Del Potro, who defeated Roger Federer in the Swiss Indoors final last week, also cruised into the next round with a straightforward 6-2, 6-2 win over Alejandro Falla.
"I feel tired, but this tournament is so good," he said. "It's a big tournament, and I'm ready to do my best like in Basel and Vienna. "I played really well today. Tomorrow, I have a difficult match against a French guy."
David Ferrer progressed with a straight set victory over Marcel Granollers, but American John Isner's outside chance of making the ATP World Tour Finals ended with a second round 6-4, 7-6 (5) loss to wildcard Michael Llodra.