Jo-Wilfried Tsonga had little explanation for his poor showing as he made his earliest grand slam exit in more than five years at the US Open today.
The fifth seed crashed out in the second round to unheralded Slovakian Martin Klizan, putting in an error-strewn display to go down 6-4 1-6 6-1 6-3.
Not since the Australian Open in 2007 had Tsonga, who had been expected to meet Andy Murray in the quarter-finals, lost before the third round in one of the sport's biggest four tournaments.
The Frenchman said: "In the second set I played well. But at the beginning of the second set also it was dangerous for me, and finally I came back.
"Today I was not in good shape. I didn't play good tennis. It seemed like I couldn't hit the ball hard enough to put my opponent out of position. I don't really know why it was like this today, but sometimes it happens with me.
"I'm disappointed but it's tennis. Sometimes you win, sometimes you lose. Of course, it's always sad when you lose but I will wait for another good moment. I will forget it."
Tsonga, a quarter-finalist here last year and a semi-finalist at Wimbledon last month, looked like he had turned things around in the second set but instead Klizan pulled away again in the third.
The Slovakian then opened up a 4-0 lead in the fourth set and, although Tsonga responded to reduce the deficit to 4-3, it was not good enough.
The 27-year-old denied he was carrying any injuries, although fatigue is clearly taking its toll on a lot of players, while he admitted the dominance of the top four in men's tennis can be dispiriting.
He said: "We have to play every week. I'm not a machine. Sometimes I'm tired, sometimes not. Sometimes in good shape, sometimes not. That's it.
"I work hard every week. I give a lot of myself every day. I never get rewards. That's why sometimes it's tough."
Klizan, ranked 52nd in the world, has had a good season but had never beaten anyone close to the calibre of Tsonga before and lost to Britain's Dan Evans in the Davis Cup earlier this year.
The 23-year-old, who next meets another Frenchman, 32nd seed Jeremy Chardy, was understandably thrilled with his breakthrough victory, saying: "He's number six in the world and I beat him.
"I feel great. I'm very happy. I think it's my best result in my career and I'm looking forward to playing Saturday in the third round. There is a chance to win again."
American Mardy Fish, the 23rd seed, became the 10th player to recover from two sets down to win against Russia's Nikolay Davydenko, a new record for the US Open.
Fish proved the tougher in sweltering conditions on Arthur Ashe Stadium to win 4-6 6-7 (4/7) 6-2 6-1 6-2 while Feliciano Lopez and Marin Cilic both narrowly avoided the same fate.
Lopez, seeded 30th, beat fellow Spaniard Pablo Andujar 6-4 6-1 6-7 (5/7) 3-6 7-5 while 12th seed Cilic eventually saw off German qualifier Daniel Brands 6-3 6-2 5-7 4-6 7-5.
Eleventh seed Nicolas Almagro was another man forced to battle in hot conditions, the Spaniard beating German Philipp Petzschner 6-3 5-7 5-7 6-4 6-4, and he next faces American teenager Jack Sock, a more comfortable 6-2 6-2 6-4 winner over Flavio Cipolla.
Fish underwent minor heart surgery in May to correct an irregular heartbeat and admitted he still has doubts about his health, particularly during long, hot matches.
He said: "You're just not quite sure how you're going to turn up. The first match back was Wimbledon for me. It was a three-set match. You sort of freak yourself out a little bit.
"That part's been really hard for me. I feel fine right now. Hopefully you can draw on that type of confidence but that's been the toughest thing by far with me right now."
Sixth seed Tomas Berdych eased through 6-1 6-4 6-2 against Estonia's Jurgen Zopp and next meets America's Sam Querrey, who defeated Ruben Ramirez Hidalgo of Spain 6-3 6-4 6-3.
Another home player, James Blake, rolled back the years with a 6-1 6-4 6-2 victory over 24th seed Marcel Granollers, and the 32-year-old said: "Today's match was one of the best matches I've played in years."
In the third round Blake will meet 15th seed Milos Raonic, who put his struggles of the first round behind him to beat Paul-Henri Mathieu in straight sets.
Fernando Verdasco set up a meeting with top seed Roger Federer by defeating fellow Spaniard Albert Ramos 7-6 (7/4) 5-7 7-6 (7/5) 6-4, while France's 16th seed Gilles Simon was a 6-4 4-6 6-4 6-4 winner over Jimmy Wang.