PARIS — Needing one point for an upset win over Justine Henin at the French Open, Sam Stosur wavered, hitting a double-fault.

The Australian took a deep breath and tried again. This time she launched a confident serve into the corner, setting her up for an overhead slam to seal the biggest victory of her career.

Stosur sidelined Henin 2-6, 6-1, 6-4 in the fourth round Monday, ending the four-time French Open champion's streak of 24 consecutive victories at Roland Garros. Stosur's opponent in the quarterfinals will be top-ranked Serena Williams, who beat Shahar Peer 6-2, 6-2.

No. 3-seeded Novak Djokovic eliminated the last American in the men's draw, beating Robby Ginepri 6-4, 2-6, 6-1, 6-2.

Henin's defeat was her first in the tournament since 2004. She was seeded 22nd playing at Roland Garros for the first time since ending a 20-month retirement, and looked like a title contender in the early rounds.

But after taking a 4-3 lead in the final set against the No. 7-seeded Stosur, Henin showed signs of nerves and was betrayed by her elegant backhand.

Serving at 4-all, the Belgian double-faulted to reach break point, then yanked a backhand wide. In the final game she pushed three backhands into the net, including a potential putaway on the first point.

In the final two sets, Stosur had a 20-8 edge in winners and converted four of five break-point chances.

"I knew what I had to do," she said. "I kept going for it and I believed in myself."

As for that double-fault on the next-to-last point?

"I just tried to shake it off and tried to have a laugh at myself, not worry about it and get the next one in," Stosur said.

The 26-year-old Stosur has won 18 matches on clay this year, the most on the women's tour. She was a Roland Garros semifinalist last year and is ranked a career-best No. 7 — the highest ranking for an Australian-born woman since Wendy Turnbull in 1985.

Williams advanced easily, looking shaky only after her fourth-round victory, when she tried to speak French to the crowd.

"I get so nervous," she told the interviewer with a giggle in English when she was done. Otherwise, she advanced smoothly to the quarterfinals.

"I seem to always be able to turn it up during this particular stage," Williams said. "Hopefully I turn it up again."

She complained of dizziness from a cold following a seesaw three-set win in her previous match, but the only wobble against the No. 18-seeded Peer came at the start. Williams lost the first seven points, then swept nine in a row.

From 2-all, Williams won five consecutive games to take charge of the match.

Afterward, she was interviewed courtside by former French player Cedric Pioline.

"I love Paris," she told the crowd in French. "My game is better. I hope I'm going to win."

Stosur's win spoiled the prospect of a showdown between longtime rivals Williams and Henin. Instead, Williams will meet Stosur.

"You can never underestimate anyone, and Sam is actually a wonderful clay-court player," Williams said. "She's someone you can't overlook."

Against Djokovic, Ginepri was serving at love-1 in the third set when he went down face-first chasing a shot. He made the most of his awkward court position by doing push-ups, but lost the next two points to lose serve, and won only three games the rest of the way.

"I felt a little stupid slipping and falling on my face, so I tried to get the crowd back to my side," Ginepri said. "Maybe that took a little bit of my focus away doing that. I'll probably never do push-ups again on court."

Djokovic's next opponent will be No. 22 Jurgen Melzer, a first-time Grand Slam quarterfinalist playing in his 32nd major event. The Austrian advanced by beating qualifier Teimuraz Gabashvili 7-6 (6), 4-6, 6-1, 6-4.

On another chilly, cloudy, windy afternoon, center court was half empty for the start of Williams vs. Peer.

It didn't last long: Williams hit six aces, broke six times and won in just over an hour.

Serena's sister Venus, eliminated Sunday, watched from the stands. She did not wear a corset.

Peer fell to 0-10 against the Williams sisters, including 0-5 versus Serena. Peer is 4-22 against top-five opponents.

Serena is bidding for her 13th Grand Slam championship, and her second this year. Her lone French Open title came in 2002.

Ginepri, ranked 98th, was an unlikely round-of-16 foe for Djokovic. Ginepri entered the tournament with a 1-7 record this year, and a career record of 9-31 on clay.

Djokovic's box included more than a dozen supporters who cheered and waved a Serbian flag every time he won a point. Ginepri is without a coach and traveled to Paris by himself.

Still, the American played Djokovic on even terms for more than an hour. Ginepri held serve easily until the final game of the first set, when he was broken.

Djokovic blew an easy forehand putaway to lose his serve for the first time, and Ginepri broke again while dominating the second set.

But then Ginepri faded fast, perhaps weary after playing 13 grinding sets in his first three matches. His groundstrokes became more erratic, and Djokovic won five consecutive games and 10 of 11 to take control.

"I played really good in the third and fourth sets," said Djokovic, a two-time semifinalist at Roland Garros. "I had some really good matches on clay recently. Now I'm in the quarterfinals and I need to keep playing aggressively."