Tennis stars hit a FASHION GRAND SLAM

Models have the runway, actresses the red carpet and -- when it comes to showing off their latest styles -- tennis players have center court.

One emerging trend is to incorporate a cocktail-attire look into their performance clothes, especially if they're playing under the lights at night. And, says tennis star Maria Sharapova, there's no better place to pull out the stops than the U.S. Open -- running through Sept. 7.

"It's the place to do something fun and a little out of the box," says Sharapova, the 2006 U.S. Open champ who is nursing a shoulder injury and not competing this year. "It's the biggest crowd, and it's what people are talking about. I was fortunate to play -- and win -- in the Audrey Hepburn dress."

That dress, with its sparkly neckline, satin-bow waistline and keyhole openings down the back, started a wave of red carpet-worthy ensembles. Tiffany even outfits Sharapova in jewelry for tennis events and a collection of earrings, called Tiffany for Maria Sharapova, is sold in stores around the world.

This year, Serena Williams, who has proven at times to be a fashion rebel, has a U.S. Open dress that also has a sophisticated cocktail-dress vibe. It's red with a slim bodice, dropped waist and pleated skirt.

On the men's side, Roger Federer, who last year played night matches in a tuxedo-style outfit with a blue-and-white ensemble for day, this year was switching between a polo shirt with an emblazoned RF logo in red for day and a smoke-gray color at night.

The U.S. Open has a party atmosphere like no other Grand Slam, says Nike senior designer Colleen Sandieson. Whereas Wimbledon is traditional and Paris is more fashion-forward, fans at the U.S. Tennis Center in New York like to see the best athletes look like stars.

At the 2007 U.S. Open, Sharapova had two custom-made Nike dresses in the same silhouette, but one was white with a black graphic design on the bodice while the other was red and dotted with Swarovski crystals for nighttime play.

It was an acknowledgment of the changing conditions the day can bring: hot and steamy under the sun and cooler in the evening, Sharapova explains. The crowd's mood changes as well, with a more casual audience at daytime matches and the just-left-the-office crew at night.

Had she played this year, Sharapova would have worn a stretch velvet dress with silk on the neckline and straps.

Designers are working on a similar look for amateur athletes.

Golf-clothes designer Linda Hipp, whose label Lija is introducing tennis clothes in the spring, says an increasing number of athletic customers want to be able to wear their outfits even off the court. An evening player might be on a date or enjoying time with her spouse and might want a little more fashion in her outfit.

So while tennis dresses are unlikely to be mistaken for a bona fide cocktail frock, there's no reason not to incorporate a ruffle here or ruching there to make a flattering, flirty garment.

"Evening tennis has a more lively social component," Hipp says.

But among amateurs, the look isn't quite a grand slam yet. Nadine Wolff, an avid tennis player from Port Washington, N.Y., has a closet full of tennis clothes, but she chooses outfits based on conditions and weather -- not the time of day.

"For the real world, you wear the same type of attire day or night. ... I have a lot of tennis clothes, and I don't separate them," she says. "Maybe I do wear more white during the day, but that's because it's hot."