Tennis great Martina Navratilova (C) stands with Serena Williams (L) of the U.S. as she holds the winner's trophy next to Maria Sharapova of Russia after winning their women's singles final match at the Australian Open 2015 tennis tournament in Melbourne
January 31, 2015. REUTERS/Issei Kato (AUSTRALIA - Tags: SPORT TENNIS)

Serena Williams of the U.S. holds her trophy while flanked by tennis greats Martina Navratilova (L) and Chris Evert after Williams defeated Caroline Wozniacki of Denmark in their women's singles finals match at the 2014 U.S. Open tennis tournament in New York, September 7, 2014. REUTERS/Mike Segar (UNITED STATES - Tags: SPORT TENNIS)

Tennis great Martina Navratilova and her partner Julia Lemigova (L) celebrate after Kei Nishikori of Japan defeated Novak Djokovic of Serbia in their semi-final match at the 2014 U.S. Open tennis tournament in New York, September 6, 2014. REUTERS/Mike Segar (UNITED STATES - Tags: SPORT TENNIS)

Tennis great Martina Navratilova and her partner Julia Lemigova (L) celebrate after Kei Nishikori of Japan defeated Novak Djokovic of Serbia in their semi-final match at the 2014 U.S. Open tennis tournament in New York, September 6, 2014. REUTERS/Mike Segar (UNITED STATES - Tags: SPORT TENNIS)

Tennis great Martina Navratilova and her partner Julia Lemigova (L) celebrate after Kei Nishikori of Japan defeated Novak Djokovic of Serbia in their semi-final match at the 2014 U.S. Open tennis tournament in New York, September 6, 2014. REUTERS/Mike Segar (UNITED STATES - Tags: SPORT TENNIS)

Tennis greats John McEnroe (R) and Martina Navratilova take part in the opening ceremony at the 2014 U.S. Open tennis tournament in New York, August 25, 2014. REUTERS/Adam Hunger (UNITED STATES - Tags: SPORT TENNIS)

Tennis legend Martina Navratilova (2nd R) takes a group photo with Singapore athletes bowler Adelene Wee, swimmers Pat Chan (2nd L) and Joscelin Yeo (L) as they meet the media during Navratilova's visit to Singapore August 15, 2014. Men's tennis will see a flurry of women coaches after Andy Murray broke down a gender barrier by hiring Amelie Mauresmo, says 18-times grand slam singles champion Navratilova who is open to tutoring men. Picture taken August 15, 2014. REUTERS/Edgar Su (SINGAPORE - Tags: SPORT TENNIS) 

Tennis legend Martina Navratilova speaks as she meets the media in Singapore August 15, 2014. Men's tennis will see a flurry of women coaches after Andy Murray broke down a gender barrier by hiring Amelie Mauresmo, says 18-times grand slam singles champion Navratilova who is open to tutoring men. Picture taken August 15, 2014. REUTERS/Edgar Su (SINGAPORE - Tags: SPORT TENNIS HEADSHOT) 

Tennis legend Martina Navratilova smiles as she meets the media during her visit to Singapore August 15, 2014. Men's tennis will see a flurry of women coaches after Andy Murray broke down a gender barrier by hiring Amelie Mauresmo, says 18-times grand slam singles champion Navratilova who is open to tutoring men. Picture taken August 15, 2014. REUTERS/Edgar Su (SINGAPORE - Tags: SPORT TENNIS HEADSHOT) 

Tennis legend Martina Navratilova smiles as she meets the media during her visit to Singapore August 15, 2014. Men's tennis will see a flurry of women coaches after Andy Murray broke down a gender barrier by hiring Amelie Mauresmo, says 18-times grand slam singles champion Navratilova who is open to tutoring men. Picture taken August 15, 2014. REUTERS/Edgar Su (SINGAPORE - Tags: SPORT TENNIS HEADSHOT) 

Actress Keira Knightley (CENTRE L), her husband James Righton (C) and former tennis champion Martina Navratilova (R) sit on Centre Court at the Wimbledon Tennis Championships in London July 5, 2014. REUTERS/Andy Rain/Pool(BRITAIN - Tags: ENTERTAINMENT SPORT TENNIS)

Actress Keira Knightley (CENTRE L) and her husband James Righton (C) speak to former tennis player Martina Navratilova (R) on Centre Court at the Wimbledon Tennis Championships in London July 5, 2014. REUTERS/Andy Rain/Pool(BRITAIN - Tags: ENTERTAINMENT SPORT TENNIS)

Former tennis players Martina Navratilova
(L) and Billie Jean King (C) sit on Centre Court for the women's singles final tennis match between Marion Bartoli of France and Sabine Lisicki of Germany at the Wimbledon Tennis Championships, in London July 6, 2013. REUTERS/Suzanne Plunkett (BRITAIN - Tags: SPORT TENNIS)

Former tennis player Martina Navratilova
(R) sits on Centre Court for the women's singles final tennis match between Marion Bartoli of France and Sabine Lisicki of Germany at the Wimbledon Tennis Championships, in London July 6, 2013. REUTERS/Suzanne Plunkett (BRITAIN - Tags: SPORT TENNIS)

A pedestrian walks across a rainbow pedestrian crossing painted on Sydney's Oxford street, the city's main gay district April 4, 2013. Officials have ordered the removal of the rainbow pedestrian crossing painted on a street in Sydney's main gay district, setting off fierce debate in a city known for its annual Mardi Gras gay pride event, one of Australia's main tourist draws. Controversy over the crossing, painted in February to celebrate the 35th anniversary of the annual gay festival, is pitting those proud of Sydney's reputation for tolerance, such as gay former tennis star Martina Navratilova, against government officials who say it is a safety hazard. Picture taken April 4, 2013. REUTERS/David Gray (AUSTRALIA - Tags: SOCIETY TPX IMAGES OF THE DAY) 

People walk across a rainbow pedestrian crossing painted on Sydney's Oxford street, the city's main gay district April 4, 2013. Officials have ordered the removal of the rainbow pedestrian crossing painted on a street in Sydney's main gay district, setting off fierce debate in a city known for its annual Mardi Gras gay pride event, one of Australia's main tourist draws. Controversy over the crossing, painted in February to celebrate the 35th anniversary of the annual gay festival, is pitting those proud of Sydney's reputation for tolerance, such as gay former tennis star Martina Navratilova, against government officials who say it is a safety hazard. Picture taken April 4, 2013. REUTERS/David Gray (AUSTRALIA - Tags: SOCIETY) 

Former tennis players Martina Navratilova (front) and Mary Pierce wave as they arrive on Centre Court for the women's singles tennis match between Serena Williams of the U.S. and Zheng Jie of China at the Wimbledon tennis championships in London June 30, 2012. REUTERS/Stefan Wermuth (BRITAIN - Tags: SPORT TENNIS)

Former tennis player Martina Navratilova (L top) watches the women's singles final match between Sara Errani of Italy and Maria Sharapova of Russia during the French Open tennis tournament at the Roland Garros stadium in Paris June 9, 2012. REUTERS/Gonzalo Fuentes (FRANCE - Tags: SPORT TENNIS)

Former tennis players Martina Navratilova (L) and Jana Novotna (2ndL) serve to Nathalie Tauziat (3rdL) and Sandrine Testud (4thL) during an exhibition match on an ephemeral pink clay court to celebrate Women's Day during the French Open tennis tournament at the Roland Garros stadium in Paris June 7, 2012. REUTERS/Regis Duvignau (FRANCE - Tags: SPORT TENNIS ENTERTAINMENT)

Former tennis players Martina Navratilova (bottom R) and Jana Novotna (botom L) serve to Nathalie Tauziat (top R) and Sandrine Testud (top L) during an exhibition match on an ephemeral pink clay court to celebrate Women's Day during the French Open tennis tournament at the Roland Garros stadium in Paris June 7, 2012. REUTERS/Regis Duvignau (FRANCE - Tags: SPORT TENNIS ENTERTAINMENT)

Former tennis players (L-R) Nathalie Tauziat, Sandrine Testud, Jana Novotna, Chris Evert and Martina Navratilova pose with French Tennis Federation (FFT) President Jean Gachassin (3rdR) on an ephemeral pink clay court to celebrate Women's Day during the French Open tennis tournament at the Roland Garros stadium in Paris June 7, 2012. REUTERS/Regis Duvignau (FRANCE - Tags: SPORT TENNIS ENTERTAINMENT)

John McEnroe (R) and his teammates Chris Evert (C) and Martina Navratilova are seen during an exhibition match at the Family Circle Cup tennis tournament in Charleston, South Carolina April 7, 2012. REUTERS/Mary Ann Chastain (UNITED STATES - Tags: SPORT TENNIS) 

Tennis player Martina Navratilova (L) poses for photographs as she arrives for the Laureus World Sports Awards 2012 in central London February 6, 2012. REUTERS/Paul Hackett (BRITAIN - Tags: ENTERTAINMENT SOCIETY SPORT) 

Britain's Prime Minister David Cameron (FRONT C) poses for a photograph with sports personalities (BACK L - R) Sean Fitzpatrick, Gary Player, Nadia Comaneci, Novak Djokovic, Boris Becker, Oscar Pistorius, Steve Regrave, Mark Spitz; (FRONT L-R) Kelly Holmes, Tanni Grey-Thompson, David Cameron, Edwin Moses and Martina Navratilova, during a reception for the 2012 Laureus Awards in 10 Downing Street in central London February 6, 2012. REUTERS/Olivia Harris (BRITAIN - Tags: POLITICS SOCIETY SPORT) 

Britain's Prime Minister David Cameron (FRONT C) poses for a photograph with sports personalities (BACK L - R) Sean Fitzpatrick, Gary Player, Nadia Comaneci, Novak Djokovic, Boris Becker, Oscar Pistorius, Steve Regrave, Mark Spitz; (FRONT L-R) Kelly Holmes, Tanni Grey-Thompson, David Cameron, Edwin Moses and Martina Navratilova, during a reception for the 2012 Laureus Awards in 10 Downing Street in central London February 6, 2012. REUTERS/Olivia Harris (BRITAIN - Tags: POLITICS SOCIETY SPORT) 

Britain's Prime Minister David Cameron talks to tennis player Martina Navratilova during a reception for the 2012 Laureus Awards in 10 Downing Street in central London February 6, 2012. REUTERS/Olivia Harris (BRITAIN - Tags: POLITICS SOCIETY SPORT TENNIS) 

Former Wimbledon champion Martina Navratilova stands on Centre Court for the presentation after the finals match between Maria Sharapova of Russia and Petra Kvitova of the Czech Republic at the Wimbledon tennis championships in London July 2, 2011. REUTERS/Stefan Wermuth (BRITAIN - Tags: SPORT TENNIS)

Former Wimbledon champion Martina Navratilova stands on Centre Court for the presentation after the finals match between Maria Sharapova of Russia and Petra Kvitova of the Czech Republic at the Wimbledon tennis championships in London July 2, 2011. REUTERS/Stefan Wermuth (BRITAIN - Tags: SPORT TENNIS)

Former Wimbledon champion, Martina Navratilova, waves as she arrives on Centre Court for the match between Caroline Wozniacki of Denmark and Jarmila Gajdosova of Australia at the Wimbledon tennis championships in London June 25, 2011. REUTERS/Stefan Wermuth (BRITAIN - Tags: SPORT TENNIS)

Elton John and Martina Navratilova celebrate scoring a point against Steffi Graf and Andre Agassi during their mixed doubles game at the World Team Tennis Smash Hits fundraiser in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES - Tags: SPORT ENTERTAINMENT TENNIS) 

Elton John and Martina Navratilova celebrate scoring a point against Steffi Graf and Andre Agassi during their mixed doubles game at the World Team Tennis Smash Hits fundraiser in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES - Tags: SPORT ENTERTAINMENT TENNIS) 

Billie Jean King (L) and Martina Navratilova speak at a news conference for the World Team Tennis Smash Hits fundraiser in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES - Tags: SPORT ENTERTAINMENT TENNIS IMAGES OF THE DAY) 

Martina Navratilova speaks at a news conference for the World Team Tennis Smash Hits fundraiser in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES - Tags: SPORT ENTERTAINMENT TENNIS) 

Martina Navratilova (R) speaks at a news conference for the World Team Tennis Smash Hits fundraiser, as Billie Jean King listens, in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES - Tags: SPORT ENTERTAINMENT TENNIS) 

Martina Navratilova attends a news conference for the World Team Tennis Smash Hits fundraiser in Washington November 15, 2010. The event will raise money for the Elton John AIDS Foundation and local Washington, D.C. Area AIDS charities, according to the World Team Tennis website. REUTERS/Joshua Roberts (UNITED STATES 

Former tennis stars Martina Navratilova (L) and Chris Evert wave to fans before the women's finals match between Vera Zvonareva of Russia and Kim Clijsters of Belgium during the U.S. Open tennis tournament in New York, September 11, 2010. REUTERS/Jessica Rinaldi (UNITED STATES - Tags: SPORT TENNIS) 

Former tennis stars Chris Evert (2nd L) and Martina Navratilova (2nd R) pose with Kim Clijsters (L) of Belgium and Vera Zvonareva of Russia before the women's finals match during the U.S. Open tennis tournament in New York, September 11, 2010. REUTERS/Shannon Stapleton (UNITED STATES - Tags: SPORT TENNIS) 

Former tennis stars Martina Navratilova (L) and Chris Evert talk before the women's finals match between Vera Zvonareva of Russia and Kim Clijsters of Belgium, during the U.S. Open tennis tournament in New York, September 11, 2010. REUTERS/Mike Segar (UNITED STATES - Tags: SPORT TENNIS) 

Former tennis star Martina Navratilova waves to the crowd as she is honored during the opening ceremony of the U.S. Open tennis tournament in New York August 30, 2010. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT TENNIS PROFILE) 

Martina Navratilova smiles after meeting Britain's Queen Elizabeth at the Queen attends the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club in London June 24, 2010.REUTERS/Pool/Oli Scarf (BRITAIN - Tags: SPORT TENNIS ROYALS ENTERTAINMENT) 

Britain's Queen Elizabeth shakes hands with Martina Navratilova, while other players line up to greet her as she attends the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club in London June 24, 2010. It is the first visit by Queen Elizabeth to the Championships in 33 years. REUTERS/Pool/Oli Scarf (BRITAIN - Tags: SPORT TENNIS ROYALS ENTERTAINMENT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: HEADSHOT SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: SPORT) 

Tennis legend Martina Navratilova poses for a portrait in New York April 7, 2010. Navratilova has been diagnosed with breast cancer, she has told U.S. online magazine People. She was diagnosed with a non-invasive form of breast cancer called ductal carcinoma in situ, or DCIS, which in her case had not spread to the breast tissue. REUTERS/Lucas Jackson (UNITED STATES - Tags: HEADSHOT SPORT IMAGES OF THE DAY) 

Tennis great Martina Navratilova of the U.S. returns a shot to Monica Seles during their demonstrative match at the BCR Open Romania tennis tournament in Bucharest in this September 16, 2007 file photo. Navratilova, one of the finest female tennis players of all time, has been diagnosed with breast cancer, she has told U.S. magazine People. REUTERS/Mihai Barbu/Files (ROMANIA - Tags: SPORT TENNIS HEALTH) 

Martina Navratilova of the U.S. is introduced before playing an exhibition doubles match with Justine Henin of Belgium, Steffi Graf of Germany and Lindsay Davenport of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, in this March 12, 2010 file photograph. Navratilova, one of the finest female tennis players of all time, has been diagnosed with breast cancer, she has told U.S. magazine People. REUTERS/Danny Moloshok/Files (UNITED STATES - Tags: SPORT TENNIS) 

Former tennis player Martina Navratilova of the U.S. speaks at the Foreign Correspondents' Club of Japan in Tokyo in this March 11, 2008 file photograph. Navratilova, one of the finest female tennis players of all time, has been diagnosed with breast cancer, she has told U.S. magazine People. REUTERS/Kiyoshi Ota/Files (JAPAN - Tags: SPORT TENNIS HEADSHOT) 

Lindsay Davenport of the U.S. (L) talks with Steffi Graf of Germany as they plays an exhibition doubles match against Justine Henin of Belgium and Martina Navratilova of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS) 

Steffi Graf (R) of Germany hits a volley as Lindsay Davenport (L) of the U.S. looks on as they play an exhibition double match against Justine Henin of Belgium and Martina Navratilova of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS) 

Singer Tony Bennett (L) sits with his wife Susan Crow (R) as they watch Justine Henin of Belgium smiles and Martina Navratilova of the U.S. play against Steffi Graf of Germany and Lindsay Davenport of the U.S. in an exhibition doubles match during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS ENTERTAINMENT) 

Martina Navratilova of the U.S. is introduced before playing an exhibition doubles match with Justine Henin of Belgium, Steffi Graf of Germany and Lindsay Davenport of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS IMAGES OF THE DAY) 

Martina Navratilova (L) of the U.S. watches as Justine Henin of Belgium returns a shot during an exhibition doubles match against Steffi Graf of Germany and Lindsay Davenport of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS DISASTER) 

Lindsay Davenport (R) of the U.S. reacts with Steffi Graf (L) of Germany as they play an exhibition doubles match against Justine Henin of Belgium and Martina Navratilova of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS DISASTER) 

Steffi Graf of Germany reacts as she sees singer Tony Bennett on the monitor watching from the stands while she plays an exhibition doubles match during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. Graf played with with Lindsay Davenport of the U.S., Justine Henin of Belgium and Martina Navratilova of the U.S. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS DISASTER) 

Justine Henin of Belgium smiles with Martina Navratilova of the U.S. as they play against Steffi Graf of Germany and Lindsay Davenport of the U.S. during the Hit for Haiti fund raiser event at the Indian Wells WTA and ATP tennis tournament in Indian Wells, California, March 12, 2010. REUTERS/Danny Moloshok (UNITED STATES - Tags: SPORT TENNIS)