PARIS - Justine Henin kept saying it, even if no one was listening. She's not back to being the player she was before taking a 20-month hiatus from tennis. She's still searching for consistency on court. Too many "ups and downs," to use her term.

Turns out Henin was right. Betrayed down the stretch by her best stroke, the backhand, and by her usually steely nerves, the four-time French Open champion lost to No. 7-seeded Sam Stosur, of Australia 2-6, 6-1, 6-4, in the fourth round yesterday, ending Henin's 24-match winning streak at her favorite tournament.

"Everyone wants to see me at the level that I was," said Henin, who abruptly retired in May 2008 while ranked No. 1, then returned to the tour this season and reached the Australian Open finals in January. "I still have to work a lot, quite simply."

Thanks to her 2005-07 titles at Roland Garros, and then the time away, it's been 6 years since Henin felt the sting of a loss at the clay-court Grand Slam tournament - all the way back in 2004's second round.

"Obviously, beating Justine is going to give me lots and lots of confidence for the next match," said Stosur, a French Open semifinalist in 2009 and a tour-best 18-2 on clay this year. "That's obviously a great achievement for me, but it's not over yet. I'm just in the quarters and going to play the No. 1 player in the world next."

That would be Serena Williams, who stumbled at the start before cruising to a 6-2, 6-2 victory over No. 18 Shahar Peer, of Israel. Williams dropped the first seven points of the match, then immediately took nine in a row and was on her way.

"I seem to always be able to turn it up during this particular stage," said Williams, who won two of the past three Grand Slam tournaments and owns 12 major titles.

The other quarterfinal in that half of the draw will be No. 4 Jelena Jankovic against 36th-ranked Yaroslava Shvedova. Jankovic beat No. 23 Daniela Hantuchova, 6-4, 6-2, while Shvedova eliminated 107th-ranked Jarmila Groth, 6-4, 6-3.

In men's fourth-round matches, four-time champion Rafael Nadal improved to 200-16 on clay over his career by overcoming four breaks of serve to defeat No. 24 Thomaz Bellucci, 6-2, 7-5, 6-4. A year ago, Nadal lost in the fourth round - he was 31-0 at Roland Garros before that stunning exit against Robin Soderling - but he insisted that didn't make him any more careful this time.

Now Nadal will meet No. 19 Nicolas Almagro, who knocked off No. 7 Fernando Verdasco, 6-4, 1-6, 6-1, 6-4. Also, No. 3 Novak Djokovic eliminated the last U.S. man in the tournament, 98th-ranked Robby Ginepri, of Kennesaw, Ga., 6-4, 2-6, 6-1, 6-2, and No. 22 Jurgen Melzer beat 114th-ranked qualifier Teimuraz Gabashvili, 7-6 (6), 4-6, 6-1, 6-4.

At 29, Melzer is the oldest man left in the field. He's also reached his first Grand Slam quarterfinal in 32 appearances.

"Well, to be the oldest player is not a special feeling," Melzer said. "Reaching the quarterfinals for the first time - that's a special feeling."

Williams might have forgotten what it feels like to reach the semifinals in Paris: She hasn't been that far at the French Open since 2003, a year after she won her only championship at the tournament.

"I feel prepared every year, and I always dive out in the quarters," Williams said. "I'm just trying to get past that this year, hopefully."