PARIS(AP) 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.

There was no prescription to help Andy Roddick, who lost to qualifier Teimuraz Gabashvili 6-4, 6-4, 6-2. Roddick threw rackets and argued with the umpire, but the fits of temper failed to produce a turnaround against an opponent ranked 114th.

The top-ranked Williams appeared in danger when she fell behind 5-love in the second set and summoned the trainer. Soon Williams' court movement improved, her strokes steadied and she advanced to the fourth round.

The seesaw win assured Williams of retaining the No. 1 ranking after the tournament.

Top-seeded American twins Bob and Mike Bryan were upset in the second round of doubles by unseeded Brazilians Marcelo Melo and Bruno Soares, 6-3, 7-6 (6).

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.

But in the third set, Williams erased three break points to take the lead for good at 2-1. She again became aggressive with her returns, and whacked the last one at Pavlyuchenkova's feet for the win.

Pavlyuchenkova fell to 8-1 this year in three-set matches.

Roger Federer has been an adviser, friend and Olympic doubles partner for Stanislas Wawrinka, and now they'll be Grand Slam opponents for the first time. Switzerland's two best players meet Sunday in the fourth round.

He's really a good friend,'' Wawrinka said.We know each other so well, so it's never easy to play him, especially here in French Open. But then when you go on court, you try to do your job.''

Wawrinka has taken care of business at Roland Garros, reaching the round of 16 for the first time. With one more victory, he would earn his first berth in a Grand Slam quarterfinal.

A win would also end Federer's record streak of reaching the semifinals in 23 consecutive major tournaments.

All streaks come to an end,'' Wawrinka said.Sooner or later in his career, he will lose before the semifinals. But writing history, that is not my main objective.''

Seeded 20th, Wawrinka earned a chance to play Federer by beating Fabio Fognini on Friday, 6-3, 6-4, 6-1. Federer beat qualifier Julian Reister 6-4, 6-0, 6-4.

Also advancing were Rafael Nadal, Novak Djokovic, Justine Henin, Maria Sharapova and Venus Williams. Most of tennis' top players were in action because of a schedule backlog caused by rain earlier in the week.

Defending champion Svetlana Kuznetsova was upset by fellow Russian Maria Kirilenko 6-3, 2-6, 6-4. The No. 6-seeded Kuznetsova, who saved four match points in the second round, will fall out of the top 10 for the first time in four years.

You cannot play all the time great,'' Kuznetsova said.It's ups and downs. I have not been playing well this clay-court season and this season, but it happens, you know. I'll be back. I have the game. It's fine. It's just matters of time.''

Federer has yet to drop a set, but then so has Wawrinka, who considers clay his best surface. Federer is 4-1 in the friendly rivalry and easily won their most recent meeting in Madrid two weeks ago, but Wawrinka won at the Monte Carlo Masters on clay last year.

They'll face each other on a Grand Slam stage for the first time. They first met for a practice session when Wawrinka was 16 and Federer was already in the top 10.

We played for two hours,'' Wawrinka said.It was very tough. I was very nervous to begin with, but I had a lot of fun.''

Federer has since built an unrivaled resume, with a record 16 major titles and - thanks to last year's victory at the French Open - a career Grand Slam. He has also provided informal counsel to Wawrinka, Switzerland's second-best player.

I'm not his coach, but at the beginning it's like giving tips and advice,'' Federer said.I saw him growing. It's always very interesting to see how he can continue and make progress. He's no longer asking for tips, which is a good sign.''