Novak Djokovic crashed out in the second round of the BNP Paribas Masters in Paris to American Sam Querrey.
The second seed looked on course for the easiest of wins when he raced through the first set 6-0, only to let his grip on the match slip and go down 0-6 7-6 (7/5) 6-4 in just over two hours.
The Serbian dominated his opponent's serve in the first set as took three of four break points, but Querrey got it together in the next, hammering down 10 aces, while another seven followed in the decider.
Djokovic, who entered Court Central wearing a Darth Vader mask as part of his Halloween celebrations, even went 2-0 up in the second set, but failed to convert all five of his break point opportunities in the decider.
"Sam played very well, served very well," he said on the ATP website.
When asked how he felt at one set and 0-2 down, Querrey said, "It was a little embarrassing. I walked over to where Casey, my physio/chiropractor sits with my girlfriend and Casey's wife, and I said, 'I hope I can get two games in this set'.
"Once I got the two games I kind of settled down. I was like, 'Okay, that's all I want.' But then I got rolling and got more confidence and started serving better and being a little more aggressive."
Andy Murray showed no sign of the back injury that has troubled him recently as he advanced past Paul-Henri Mathieu.