The U.S. Open can always count on the best players in women's tennis showing up for its fortnight in Flushing, along with a full complement of those striving to join their ranks.

But as the sport's calendar expands and the game exacts an increasingly harsh toll on the body, more top players are growing more assertive about just saying "no" to the myriad tournaments that have made women's tennis a nearly year-round proposition.

Their ranks include American Lindsay Davenport, the world's No. 1 player, as well as former top-ranked players Justine Henin-Hardenne of Belgium and sisters Venus and Serena Williams. Motivated alternately by concerns over age, illness and injury, each has learned to cherry-pick events on the tennis calendar -- playing less, rather than more -- in an effort to strike the perfect balance between getting enough rest to heal wrenched ankles, strained backs and pulled hamstrings and competing in enough matches to maintain world-class stamina and form.

"You have to take the right decisions -- not playing too much, taking off to rest, but working hard to be ready," said Henin-Hardenne, who has played fewer tournaments this season (eight) than any woman in the top 100.

Henin-Hardenne's light schedule is an extreme example. After reaching the No. 1 ranking in October 2003, she contracted a virus that left her bedridden for several months in 2004. In her measured return this year, she has learned she can't play world-class tennis for more than three weeks at a stretch. Still, Henin-Hardenne opens play in the U.S. Open as the seventh seed, having won her second French Open in June.

At 29, Lindsay Davenport is playing her lightest schedule and best tennis in years. After reaching the final of Wimbledon, where she lost to Venus Williams in three sets, Davenport barely picked up a racket this summer because of a back strain. Still, she worked on her fitness and got plenty of treatment. It paid dividends, with Davenport winning the U.S. Open tuneup in New Haven, Conn., on Saturday.

"I'm going to play when I'm healthy, when it's right," said Davenport, who has reached the final in two of the three Grand Slam events this year (the Australian Open and Wimbledon). "I try to focus on the quality that I can bring to each tournament that I enter."

The Williams sisters have entered even fewer tournaments this year (14 for Venus, 12 for Serena), but each has a major title to show for it. Serena won the Australian Open, but struggled after spraining an ankle in the spring. She was out of shape at Wimbledon, losing in the third round, and has only entered one tournament since, withdrawing after one round in Toronto because of a sore knee.

"I had to take time off, and then my muscle got weaker," she explained. "I should have been working on it, but I didn't realize that would happen, which is really naive of me."

That said, Serena has found time to promote her new reality show; unveil a new line of lip gloss for Estee Lauder's Flirt! cosmetics line; and prepare for the 2006 launch of her clothing line. Seeded eighth, she will debut a fairly restrained tennis outfit by Nike in her opening match Monday, but it will be complemented by a pair of 13-carat diamond earrings valued at nearly $40,000.

The only women bucking the trend are the Russians and Eastern Europeans. The Americans among the top 20 (Davenport and the Williams sisters) have each entered about 14 tournaments, on average, this year. The 10 Russians and Eastern Europeans among the top 20, by contrast, have competed in an average of about 21 tournaments each.

According to former pros Tracy Austin and Pam Shriver, the young Russians seem more hungry than most women on tour. Other than Maria Sharapova, the Russian teen whose 2004 Wimbledon victory resulted in numerous endorsement deals, few Russian players have lucrative corporate deals and must live on their winnings. They also know that the ranking system looks favorably on the quantity of tennis played.

Belgium's Kim Clijsters has taken a radically different tack. So weary of mounting injuries, she has decided, at 22, to retire in two or three years.

"I'm going to give myself 200 percent for the next two more seasons after this," Clijsters said Sunday. But "in the last few years I've gotten a lot more serious injuries. I feel like everything takes a lot longer to heal, and I'm still only 22."