Tennis star Serena Williams

Venus Williams, right, and her sister Serena pose for the cameras at Eastbourne, Monday June 16, 1997 during the Direct Line Ladies Tennis Championships. Williams wanted as much grass-court play as possible before Wimbledon. She's getting it. Williams, the 16-year-old American preparing for her first appearance at the All England Club, turned down a wild card at the Eastbourne tournament in order to play in the qualifying rounds. (AP Photo/str)

Serena Willams, of the USA, prepares to serve to Dominique van Roost of Belgium in the third round of the French Tennis Open tournament at Roland Garros stadium in Paris Saturday May 30, 1998. Williams won 6-1, 6-1. (AP Photo/Lionel Cironneau)

Venus Williams, left, and her sister Serena display the Women's Doubles trophy on Centre Court at Wimbledon Monday, July 10, 2000. The Williams sisters defeated Japan's Ai Sugiyama and Julie Halard-Decugis in the final 6-3, 6-2. (AP Photo/Jytte Nielsen)

Tennis superstar Serena Williams carries the Olympic flame as a torchbearer during the 2002 Olympic Torch Relay Saturday, Dec. 8, 2001, in Ft. Laurderdale, Fla. The torch makes its journey to Salt Lake City traveling more than 13,500 miles across the United States in 65 days carried by about 11,500 torchbearers (AP Photo/Todd Warshaw, Pool)

Serena Williams, of the United States, questions a call during her match with Jennifer Capriati, of the United States, at the U.S. Open tennis tournament in New York, Tuesday, Sept. 7, 2004. (AP Photo/ Bill Kostroun)

Serena Williams returns a shot to Ashley Harkleroad during their match at the JPMorgan Chase Open tennis tournament Wednesday, Aug. 9, 2006, in Carson, Calif. Williams won the match 6-3, 6-2. (AP Photo/Mark J. Terrill)

NEW YORK, NY - SEPTEMBER 08: Serena Williams of the United States returns a shot against Anastasia Pavlyuchenkova of Russia during Day Eleven of the 2011 US Open at the USTA Billie Jean King National Tennis Center on September 8, 2011 in the Flushing neighborhood of the Queens borough of New York City. (Photo by Nick Laham/Getty Images)

US tennis player Serena Williams returns a ball to her sister Venus Williams during an exhibition match at La Macarena bullring in Medellin on November 23, 2011. Venus won 6-4, 7-6 (7/4). TOPSHOTS AFP PHOTO/Raul ARBOLEDA (Photo credit should read RAUL ARBOLEDA/AFP/Getty Images)