Tennis star Serena Williams

LONDON, ENGLAND - JUNE 21: Serena Williams of the United States serves during her first round match against Aravane Rezai of France on Day Two of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on June 21, 2011 in London, England. (Photo by Julian Finney/Getty Images)

EASTBOURNE, ENGLAND - JUNE 15: Serena Williams of USA in action against Vera Zvonareva of Russia during day five of the AEGON International at Devonshire Park on June 15, 2011 in Eastbourne, England. (Photo by Mike Hewitt/Getty Images)

LONDON - JULY 6: (FILE PHOTO) Wimbledon Champions Roger Federer of Switzerland and Serena Williams of the U.S. pose for photographs prior to attending the Wimbledon Ball at the Savoy Hotel on July 6, 2003 in London. (Photo by Alex Livesey/Getty Images) Celebrating 125 Years Of Wimbledon Please refer to the following profile on Getty Images Archival for further imagery. http://www.gettyimages.co.uk/Search/Search.aspx?EventId=115973863&EditorialProduct=Archival Fashions http://www.gettyimages.co.uk/Search/Search.aspx?EventId=115973067&EditorialProduct=Archival For further imagery also see this lightbox http://www.gettyimages.co.uk/Account/MediaBin/LightboxDetail.aspx?Id=19295855&MediaBinUserId=3936288

LONDON, ENGLAND - FILE: Serena Williams of USA celebrates a point during the Ladies Singles Final Match against Vera Zvonareva of Russia on Day Twelve of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on July 3, 2010 in London, England. It was reported that tennis star Serena Williams is recovering in a Los Angeles' Cedars Sinai Medical Center after undergoing emergency treatment on February 28 for a blood clot in her lungs March 2, 2011. (Photo by Julian Finney/Getty Images)

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)