Justine Henin's hopes of a fifth French Open title vanished with a 2-6, 6-1, 6-4 fourth-round defeat by Australian seventh seed Samantha Stosur on Monday.

Henin, a four-time champion returning to the game after a 20-month stint in retirement, looked set to canter through after sealing the opening set in 32 minutes on Court Suzanne Lenglen.

But Stosur, a semi-finalist last year, ripped through the second and although she let slip an early break in the decider she broke the Henin serve once again for a 5-4 lead and served out for the match, sealing it in an hour and 46 minutes with a confident overhead.

Stosur showed a touch of nerves when delivering a double fault, one of seven in the match, on her first match point but she made no mistake with the second.

"I can't really believe it," the 26-year-old Australian said in a courtside interview.

"(After losing the first set) I told myself to just keep going. I believed in myself."

Henin left to a standing ovation from the crowd but it will be Stosur who faces American top seed Serena Williams for a place in the semi-finals.

World No 1 Serena Williams lost the first seven points against Shahar Peer before starting up the engine and racing past the Israeli 6-2, 6-2 to reach the quarter-finals of the French Open on Monday.

The American immediately dropped her serve on Centre Court as Peer made a strong start but the 18th seed was left gasping for air as Williams blasted her way to the opening set in under half an hour.

Peer made up for an early break in the second but it proved too big an effort as she conceded the last three games, the final one to love on her own serve after one hour and seven minutes.

Next in line for Williams will be Australian seventh seed Samantha Stosur, who knocked out four-times champion Justine Henin on Court Suzanne Lenglen.

Asked whether she was surprised by the result, Serena reminded everyone the Australian was a semi-finalist here last year.

"You can never underestimate anyone, and Sam is actually a wonderful claycourt player," she said.

"I think she proved that last year, and this year I think she has only lost twice on the clay. So she is someone you cannot overlook. She has a good chance to go all the way."

Serena, however, stands in Stosur's way as she bids for a second title in Paris after her 2002 title.

"This year my game is better, I hope I am going to win. I live here, I love Paris, it's a wonderful city," the 2002 champion told a stunned crowd as she responded to a courtside interview in French.

Serbian Novak Djokovic came through a defiant start from American Robby Ginepri to win 6-4 2-6 6-1 6-2 and book his place in the French Open quarter-finals on Monday.

Ginepri, looking to mark US Memorial Day with a first career win over Djokovic, went toe-to-toe with the third seed and won his first set in five meetings against the Serbian with some sweet baseline strokes in the second set.

But Djokovic, cheered on by an entourage packed tightly into the guest box on Court Philippe Chatrier, stepped up a gear and sealed victory in two hours and 17 minutes when Ginepri netted a defensive forehand.

He will play Austrian 22nd seed Jurgen Melzer or Russian qualifier Teimuraz Gabashvili for a place in the semi-finals.

Ginepri lifted spirits at the French Open with a display of showmanship rarely seen in the game these days, but it may have cost him a place in the quarter-finals of the claycourt slam.

The 27-year-old American was left sprawling with his face in the red Parisian dust after stretching for a deft Novak Djokovic passing shot with the fourth-round match tightly poised in the second game of the third set on Court Philippe Chatrier.

To cover his embarrassment, the American performed a series of impromptu push-ups before retreating to his chair to dust himself off and try to regain his composure for the next point.

The crowd loved it, but Ginepri, who had matched the Serbian third seed shot for shot in the opening two sets, was immediately broken and never regained his momentum.

He only won three more games in the match and it is a stunt he will not be trying again.

"I felt a little stupid slipping and falling on my face, so tried to get the crowd back to my side," said Ginepri, who had just won his first set in five career meetings against Djokovic.

"You know, maybe that took a little bit of my focus away doing that. I'll probably never do push-ups again on court."

Did it change the momentum of the game?

"A little bit. It's hard to say. You never know. It's one of those things that might work for you, but today it didn't.

"If I win the next point and hold that game, then it looks great. But I think I won three games after that, so it's a no no.

Will he do it again?

"Not on court. If you come to the gym, I'll do some there for you."

Jurgen Melzer's French Open dream continued on Monday when the Austrian reached the quarter-finals of the claycourt Grand Slam with a 7-6, 4-6, 6-1, 6-4 win over Russian qualifier Teimuraz Gabashvili.

The 22nd-seeded Melzer, the first Austrian to reach the last eight in Paris since Thomas Muster in 1998, proved more consistent on another gloomy morning to prevail after two hours and 54 minutes.

Gabashvili missed three set points in the opener as he dropped his first set of the tournament but levelled the match with some eye-catching winners.

Melzer, making his first appearance in a Grand Slam last 16, then took command, cantering through the third set before breaking serve decisively in the ninth game of the fourth.

Melzer, at 29 the oldest player remaining in the men's draw, will next face World No 3 Novak Djokovic for a place in the semi-finals.

A player who likes to go to the net, Melzer could not be more different than Austrian idol Thomas Muster, who won the French Open in 1995 but never made it past the first round at Wimbledon.

"Playing wise, I mean, we are like day and night, so of course I was not imitating his style, because I just have a different game," Melzer said.

"But still, as an athlete, he was an idol. I mean, growing up playing tennis you have a No 1 in the world in your country. If that's not your idol, something is wrong with you."

Rafael Nadal snuffed out the threat of Brazil's Thomaz Bellucci on Monday, winning 6-2, 7-5, 6-4 to safely avoid any repeat of last year's shock fourth-round exit at the French Open.

Nadal, whose four-year domination at Roland Garros was ended exactly a year ago by Sweden's Robin Soderling, was pushed hard by the 22-year-old after dominating the first set but the outcome was never seriously in doubt.

The Spanish World No 2 had his serve broken four times during the two hour 33 minute contest on a packed Court Philippe Chatrier but always found a stinging response to deflate the 24th seed.

Nadal, bidding for a fifth title, will face Spanish opposition in the quarter-final, either in the shape of seventh seed Fernando Verdasco or 19th seed Nicolas Almagro.