PARIS(AP) Four three-set matches, four victories for Maria Sharapova at the French Open.

The unseeded Russian with the injured right shoulder pulled out another close one at Roland Garros on Sunday, coming back to beat 25th-seeded Li Na of China 6-4, 0-6, 6-4 and reach the quarterfinals at the clay-court major for the fourth time in her career.

If it takes three sets, if it takes two sets, if it takes two sets in five hours - I don't care,'' Sharapova said.I'm willing to be out there for as long as I need to be in order to finish the match.''

Sharapova was absent from the tour for the better part of year. The last Grand Slam tournament she played before her injury forced her off the court was at Wimbledon, where she lost in the second round. She then had shoulder surgery in October.

I'm definitely a little bit- little sore, but I'll be fine,'' Sharapova said.That's why the Grand Slams are great. You have a day in between, day to recover, and that always helps the body.''

On Sunday, it was Sharapova's mental strength that impressed Li more than her physical prowess.

She was always fighting, doesn't matter how was the score,'' said Li, who was up a break in the third set.I lost the first set, win second set easy, and then 4-2 up (in the third). Then maybe I lose a little bit concentration.''

Besides her ailing shoulder, Sharapova also called for a trainer to look at her left thigh after breaking Li to 4-3 in the third.

``My thigh just was a little bit sore. I just needed to put some hot cream on it to forget that anything was wrong,'' said Sharapova, who can complete a career Grand Slam by winning the French Open title.

But the thought of winning her fourth major title isn't getting to her just yet.

``I think expectations are just words, and so is pressure,'' said the 22-year-old Sharapova, who has dropped to No. 102 in the rankings because of her injury layoff.

``I'm here to get the job done, and my job isn't done.''

---=

WILLIAMS SISTERS LOSE: Venus and Serena Williams were upset in the third round of the French Open women's doubles tournament Sunday, wasting a match point and losing 7-6 (4), 5-7, 7-6 (6) to Bethanie Mattek-Sands of the United States and Nadia Petrova of Russia.

No one is ever happy to lose,'' Serena said.We could have played better.''

The Williams sisters won the French Open in 1999, one of their eight Grand Slam doubles titles.

On Sunday, Venus served for the match at 6-5 in the third set, but she was broken. In the tiebreaker, the sisters held a 6-5 lead - one point from victory - but Mattek-Sands and Petrova won the last three points of the match.

It doesn't get much tighter than that,'' Mattek-Sands said.If we can grind through that, we can really grind through anything. I'm not saying that we're going to win, but we definitely have the chance to.''

Mattek-Sands and Petrova face top-seeded Cara Black of Zimbabwe and Liezel Huber of the United States in the quarterfinals.

---=

SODERLING AND BORG: After ending Rafael Nadal's bid for a record fifth consecutive French Open title, Sweden's Robin Soderling was expecting to hear from a certain countryman who was a fairly good tennis player himself: Bjorn Borg.

After all, Sunday's result means Borg and Nadal remained tied with four straight titles at Roland Garros.

I'm not going to call him,'' Soderling said.Hopefully he will call me. That would be great.''

His 6-2, 6-7 (2), 6-4, 7-6 (2) victory over the top-seeded Nadal put Soderling in the quarterfinals at a Grand Slam tournament for the first time.

I played exactly the way I wanted to play before the match,'' Soderling said.I served well, extremely well, and that really, really helped me today.''

Mats Wilander, Sweden's Davis Cup captain and a three-time French Open champion, liked what he saw from Soderling.

``It's really nice to see some guy stand up to Nadal mentally, and be in Rafa's face a little more than other guys are doing,'' Wilander said.

---=

Associated Press Writer Trung Latieule contributed to this report.