Maria Sharapova of Russia in action during her fourth round match against Flavia Pennetta of Italy at the BNP Paribas Open tennis tournament in Indian Wells, California, USA, 17 March 2015. EPA/MIKE NELSON

Maria Sharapova of Russia serves to Jarmila Gajdosova of Australia during their first second round match of the Italian Open tennis tournament at the Foro Italico in Rome, Italy, 12 May 2015. EPA/ETTORE FERRARI

Maria Sharapova of Russia in action against Kaia Kanepi of Estonia during their first round match for the French Open tennis tournament at Roland Garros in Paris, France, 25 May 2015. EPA/ROBERT GHEMENT

Maria Sharapova of Russia in action against Irina-Camelia Begu of Romania during their third round match for the Wimbledon Championships at the All England Lawn Tennis Club, in London, Britain, 03 July 2015. EPA/FACUNDO ARRIZABALAGA

Maria Sharapova of Russia reacts in play against Ekatarina Makarova of Russia in their semi-finals match at the Australian Open Grand Slam tennis tournament in Melbourne, Australia, 29 January 2015. The Australian Open tennis tournament, the first Grand Slam of the year, runs until 01 February 2015. EPA/FILIP SINGER