Djokovic: I have no excuses
Novak Djokovic could offer no explanation for his shock third-round defeat to German Philipp Kohlschreiber in the French Open.
The fourth seeded Serbian was upset 6-4 6-4 6-4 by the 29th seed, who has never previously progressed past round two at Roland Garros.
Djokovic was installed by many as second favourite for the title, behind reigning four-time champion Rafael Nadal, given his impressive clay-court campaign this year, but was punished for an error-prone display on Court One.
The 22-year-old dubbed it "a bad day at the office", insisting tiredness was not a factor in his defeat.
"My first two matches went well and I felt good before this match," said Djokovic, who reached the semi-finals here for the last two years.
"Suddenly, it was a different story on the court. I can't really explain why.
"I was too passive and he played really solid. You have to give him credit for playing tactically smart. Unfortunately I had no solutions."
Djokovic, who played in four of the six tournaments prior to Roland Garros, added: "Mentally I'm a little bit exhausted but that's still not an explanation for my loss today.
"I'm one of the favourites to get far in the tournament. This cannot happen."
Kohlschreiber labelled his performance one of the best in his career in a big tournament.
"Everything came together," he said. "Maybe Novak didn't play his best today but every choice I made went on my side."
Kohlschreiber, whose best previous displays at a grand slam have been two last-16 appearances at the Australian Open, will play Spain's Tommy Robredo next. The 16th seed beat Argentina's Maximo Gonzalez 4-6 7-5 6-1 6-0.
Second seed Roger Federer was also in trouble early in his third round match but managed to turn things around to claim a 4-6 6-1 6-4 6-4 over Frenchman Paul-Henri Mathieu.
It was the second successive match in which Federer was taken to four sets, following on from his distinctly unimpressive display in his win over Jose Acasuso.
The Swiss recovered well, though, and can prepare for a last-16 clash with unseeded German Tommy Haas, a 7-5 6-3 4-6 6-4 winner over another Frenchman, Jeremy Chardy.
Andy Roddick had earlier put his Roland Garros demons behind him to finally make the fourth round.
The sixth seed posted a 6-1 6-4 6-4 victory over Frenchman Marc Gicquel on Suzanne Lenglen court to continue his terrific streak this week.
The American has gone out in the first round in his last two appearances here, in 2006 and 2007, but this week he is disproving the theory he is not a clay-court performer and has yet to drop a set in three matches.
"If you take away this tournament, I have a pretty good clay-court CV," said the 2003 US Open champion, whose best outing at Roland Garros had come in his opening visit, in 2001, when he made the third round.
"I certainly felt capable of making the second week of this event."
Roddick, the 2003 US Open champion and a three-time grand-slam runner-up, added: "I feel like I'm moving a little bit better on this stuff."
Gael Monfils, the 11th seed and a semi-finalist here last year, will be Roddick's next opponent after the Frenchman beat Jurgen Melzer 6-2 4-6 6-3 6-1.
Fifth seed Juan Martin del Potro advanced into the last 16 with an impressive straight-sets victory over Igor Andreev.
Away from the showcourts again today, Del Potro secured a 6-4 7-5 6-4 win on Court Two and will play ninth seed Jo-Wilfried Tsonga next.
The popular Frenchman delighted the crowd on Philippe Chatrier court as he eased to a 6-2 6-2 6-2 rout of Belgium's Christophe Rochus.