Novak Djokovic crashed out in the second round of the BNP Paribas Masters in Paris to American Sam Querrey on Wednesday.
The world No 23, who lost his opening four service games, appeared to be heading for the exit door before conjuring up a remarkable fightback to beat the No 2 seeded Serb 0-6 7-6 (7-5) 6-4 in two hours and seven minutes.
After winning just 11 points during the first eight games, the 25-year-old from Las Vegas suddenly discovered his range - particularly with his serve - to secure his first ever victory against a player ranked in the world's top three.
He collected his first break in game four of the second set, before edging the tie-break on his first set point.
The only break of the final set came in game five, although Querrey was pushed to the limit when serving at 4-3.
From 15-40 down, he went on to save four break points before sealing a famous triumph on his second match point when the five-time Grand Slam winner could only push another fierce Querrey serve beyond his opponent's baseline.
Despite the defeat, Djokovic will end the season as world no 1, and will replace Roger Federer at the top of the rankings next week.
Querrey fired 18 aces to five from his opponent whose defeat leaves Andy Murray as the highest seed left in the tournament.
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."
Fourth seed David Ferrer dispatched fellow Spaniard Marcel Granollers 6-1 6-3, taking five of his six break point chances.
Two seeds went out, though, number 10 John Isner losing 6-4 7-6 (7/5) to home favourite and wildcard Michael Llodra, while French 12th seed Richard Gasquet went down 7-6 (7/5) 4-6 6-1 to South Africa's Kevin Anderson.
Argentina's seventh seed Juan Martin Del Potro saw off Colombia's Alejandro Falla 6-2 6-2.
Serbian Janko Tipsarevic, the eighth seed, was a 6-4 7-6 (7/0) winner over Holland's Igor Sijsling, while ninth-seeded Spaniard Juan Monaco beat Bulgaria's Grigor Dimitrov 7-6 (7/4) 6-2.
Nicolas Almagro, the 11th seed, and Gilles Simon also progressed.
In the final game of the night, Canada's Milos Raonic came from a set down to see off France's Jeremy Chardy 6-7 (4/7) 7-6 (7/4) 6-3.
