Amelie Mauresmo once more crumbled like a clay figurine at the French Open on Sunday, beaten in the fourth round by a Czech teenager nearly 10 years her junior.

• Images from day eight

Nicole Vaidisova embarrassed the world number one 6-7, 6-1, 6-2, exposing the fragility of the 26-year-old Frenchwoman who has never gone beyond the quarter-finals of her home Grand Slam.

Earlier Dinara Safina upset fellow Russian Maria Sharapova [Images], women's fourth seed, while Roger Federer [Images], David Nalbandian Justine Henin-Hardenne and Kim Clijsters [Images] strolled into the last eight.

Switzerland's [Images] Martina Hingis [Images] was locked at one-set all with Israeli Shahar Peer when bad light stopped play.

Mauresmo's latest failure, however, overshadowed it all.

Vaidisova lost 6-1, 6-1 to the Frenchwoman at the same stage of the Australian Open which Mauresmo won in January but nothing comes easily to her in Paris and after leading 5-2 in the first set her strength seemed inexplicably to drain away.

She scrambled through the tiebreak but after that barely won a game as Vaidisova's fearless hitting left the 15,000 mainly French supporters packed into the steepling centre court dumb with deja vu.

By the end Mauresmo's face was taut with tension and Vaidisova put her out of her misery with a conclusive backhand winner. Almost guiltily, the 17-year-old Czech dropped her racket and fell to her knees as if to ask forgiveness from the crowd.

"It's a little bit difficult to really explain and know what exactly happened to me right now," Mauresmo said. "It's a difficult moment, but that's the way it is and it happens.

"I just played with less intensity, so that she was able to come in and play much better.

"Maybe people shouldn't expect much of me on clay."

Mauresmo could probably learn something from her conqueror. "I was in my little zone," said Vaidisova, whose next opponent is American Venus Williams [Images]. "It's my first ever quarter-final in a grand slam so I'm very excited."

Safina won a ferocious Russian catfight against Sharapova to reach her first grand slam quarter-final too.

She looked beaten when she trailed 5-1 in the final set but the 20-year-old rattled off six successive games to complete a spectacular 7-5, 2-6, 7-5 victory over the 2004 Wimbledon champion on Court Suzanne Lenglen.

"She picked up her game a little bit and mine went down -- it's not a good combination," a miffed Sharapova said. "You go into a different world and you make dumb decisions."

THREW UP

Federer looked distinctly more comfortable on centre court than rival Rafael Nadal [Images] had the previous day, purring to a 6-3, 6-2, 6-3 win over Czech Tomas Berdych.

Berdych beat Federer at the 2004 Olympics [Images] but although he briefly led 3-0 in the third set, the Swiss world number one reeled off six games in succession to keep his quest for the only grand slam title he does not possess on track.

"I felt very calm and I had a good feeling here today," said Federer. "From here on my form is only going to get better."

In the last eight he plays Croatian Mario Ancic who overcame cramp and threw up before knocking out Spanish seventh seed Tommy Robredo 6-4, 4-6, 2-6, 6-4, 7-5.

Williams kept American interest in the singles alive when she recovered from a slow start to beat Switzerland's Patty Schnyder 4-6, 6-3, 6-2.

Defending champion Henin-Hardenne withstood a late revival by 2004 champion Anastasia Myskina [Images] of Russia [Images] to win their last-16 showdown 6-1, 6-4.

Her compatriot Clijsters thumped slender Slovak Daniela Hantuchova [Images] 6-1 6-4. She is yet to drop a set and will face Hingis next if the Swiss player thwarts Peer's bid to become Israel's first women's grand slam quarter-finalist.

That is far from certain, however. Hingis won the first set 6-3 but dropped her first set of the tournament when Peer dominated the second 6-2.

Safina faces another Russian, Svetlana Kuznetsova, in the last eight. Kuznetsova beat Italian ninth seed Francesca Schiavone 1-6, 6-4, 6-4.

Men's third seed David Nalbandian powered past compatriot Martin Vassallo Arguello 6-4, 6-4, 6-4 to set up a meeting with Russian Nikolay Davydenko, who knocked out 2004 champion Gaston Gaudio of Argentina 6-3, 6-4, 3-6, 6-3.

In the men's third round French 19-year-old Gael Monfils reached the last 16 of a grand slam for the first time with a 6-2, 6-7, 7-6, 5-7, 6-4 upset of the last American in the men's singles, eighth seed James Blake.

It was Monfils's third consecutive five-set win. "He's the best athlete I've played against," the American said

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