PARIS -- Serena Williams looked ill, and not only because she had lost five games in a row at the French Open.
A trainer paid Williams a visit during a changeover, checked her temperature and gave her pills. Then came a third-set surge, and Williams beat 18-year-old Russian Anastasia Pavlyuchenkova on Saturday, 6-1, 1-6, 6-2.
The top-ranked Williams appeared in danger when she fell behind 5-love in the second set and summoned the trainer.
"I felt really dizzy out there," she said. "Just ran out of a little energy out there, just fighting a cold and fighting sickness."
Soon Williams' court movement improved, her strokes steadied and she advanced to the fourth round.
"Doesn't matter the score, especially against her," Pavlyuchenkova said. "She's a good fighter. She's really confident and she is Serena."
The third-round showdown between four-time champion Justine Henin and Maria Sharapova was suspended because of darkness at one set apiece. Henin led 6-2, but her streak of 40 consecutive sets won at Roland Garros ended when Sharapova took the second set, 6-3.
Williams' seesaw win assured her of retaining the No. 1 ranking after the tournament.
The 18th-seeded Peer had previously advanced to the fourth round twice in Paris. She broke the No. 13 Bartoli four times and had 30 winners to extend her record against her French rival to 7-2.
Petrova plays Venus Williams next.
On a cloudy, windy, chilly day, the center-court stadium was slow to fill for Williams' match, the first on the schedule.
Her aggressive returns had Pavlyuchenkova's serve under constant pressure early, but the talented young Russian -- a three-time Grand Slam champion in juniors -- suddenly reversed the momentum in the second set.
Williams began to look sluggish during points, took her time between them and occasionally grimaced, while Pavlyuchenkova's booming groundstrokes had her on the defensive.
The pills the trainer gave Williams provided a remedy.
"I don't what they were, to be honest," she said. "I just took them. He said they can help me feel better."
In the third set, Williams erased three break points to take the lead for good at 2-1.
"Definitely a weird match," Williams said. "I played all right. I definitely wasn't at my best. I just was happy to win, especially against a player that's on the up and up."
Williams again became forceful with her returns, and whacked the last one at Pavlyuchenkova's feet for the win.
"In the third, she just started the set with a new power," Pavlyuchenkova said.
Pavlyuchenkova, seeded 29th, fell to 8-1 this year in three-set matches. Williams is 100-44 in three-setters.
"After she beat me she has to win the tournament," Pavlyuchenkova said. "I really hope so."
Information from The Associated Press was used in this report.