Novak Djokovic, from Serbia, crashed out of the French Open at the third-round stage today after he lost in straight sets to Philipp Kohlschreiber on Court One.

The German 29th seed was a 6-4, 6-4, 6-4 winner over Djokovic, who has reached the semi-finals at Roland Garros for the past two years.

The result is even more of a surprise given the Serb's great clay-court campaign, which has seen him win a title in Belgrade, make two finals - in Monte Carlo and Rome - and reach a semi-final in Madrid.

Kohlschreiber, who had previously never gone further than the second round here, will play Tommy Robredo next, after the Spaniard beat Maximo Gonzalez, of Argentina, 4-6, 7-5, 6-1, 6-0.

Meanwhile, Roger Federer, the second seed, reached the last 16 but had to come from a set down to overcome Paul-Henri Mathieu of France, 4-6, 6-1, 6-4, 6-4. The Swiss will play Tommy Haas of Germany for a place in the quarter-finals.

Andy Roddick reached the last 16 at the French Open for the first time in his career on Saturday by defeating France's Marc Gicquel 6-1, 6-4, 6-4.

It was a stunning turnaround in fortunes on clay for the former world No.1 who went out in the first round here in 2006 and 2007 before missing last year's tournament with a shoulder injury.

The win made him just the second American through to fourth round at the French Open since Andre Agassi in 2003, Robbie Ginepri having achieved the feat last year.

"I played very well," Roddick said. "I knew the crowd would not be for me but they were very respectful. It's a lot better than I have done here before but it's only three matches." He will face Gael Monfils after the No 11 seed from France beat Juergen Melzer, of Austria, 6-2, 4-6, 6-3, 6-1.

The American was joined in the last 16 by Juan Martin Del Potro after a 6-4, 7-5, 6-4 win over the No 25 seed Igor Andreev, of Russia.

Del Potro will face France's Jo-Wilfried Tsonga in the quarter-finals after the No 9 seed from France beat Christophe Rochus, of Belgium, 6-2, 6-2, 6-2.

Serena Williams overcame a sluggish start to beat Spain's Maria Jose Martinez Sanchez 4-6, 6-3, 6-4 and reach the fourth round of the French Open on Saturday.

The American second seed will next face Canada's Aleksandra Wozniak, seeded 24th, for a place in the last eight.

Martinez Sanchez bagged an ill-tempered opening set after breaking in the fifth game with a controversial shot which appeared to have bounced off her arm.

Annoyed with the call, Williams went on to level the contest and her opponent eventually ran out of steam, bowing out after two hours 11 minutes on the first match point.

Svetlana Kuznetsova's pursuit of a maiden French Open title continues after she reached the fourth round by dispatching Hungary's Melinda Czink 6-1 6-3 with clinical efficiency.

The seventh seed was one of the in-form players coming into the championships, and true to form she has now progresseds into the last 16 for the sixth year running.

Czink lost the first set in only 22 minutes, and put up minimal resistance in the second. Kuznetsova was never in danger, and smashed the ball away on match point to seal a last-16 date with Polish 12th seed Agnieszka Radwanska or Ukrainian Kateryna Bondarenko.

Kuznetsova's countrywoman and the competition's fourth seed Elena Dementieva was knocked out by Australian 30th seed Samantha Stosur who won 6-3, 4-6, 6-1. Stosur will play either Italy's Tathiana Garbin or France's Virginie Razzano for a place in the quarter-finals.

The No 5 seed, Jelena Jankovic, of Serbia, eased into last 16 with a 6-1, 6-1 win over Australia's Jarmila Groth.