French tennis player Gael Monfils in action against Spaniard Marcel Granollers during their second round match for the Madrid Open tennis tournament at the Caja Magica pavilion, in Madrid, Spain, 06 May 2015. EPA/ALBERTO MARTIN

Bulgaria’s Grigor Dimitrov returns the ball to Italy’s Fabio Fognini during their second round match at the Mutua Madrid Open tennis tournament in Madrid, Spain, 06 May 2015. EPA/JUANJO MARTIN

Serena Williams of the USA returns the ball to Victoria Azarenka of Belarus during their third round match at the Mutua Madrid Open tennis tournament in Madrid, Spain, 06 May 2015. EPA/CHEMA MOYA

Swiss tennis player Roger Federer returns a ball to Austrian Nick Kyrgios during their Madrid Open tennis tournament second round match at the Caja Magica pavilion, in Madrid, Spain, 06 May 2015. EPA/JUANJO MARTIN

Australian tennis player Nick Kyrgios reacts during his Madrid Open tennis tournament second round match against Swiss Roger Federer at the Caja Magica pavilion, in Madrid, Spain, 06 May 2015. EPA/JUANJO MARTIN

Serbian tennis player Ana Ivanovic serves the ball to Spanish Carla Suarez during their Madrid Open tennis tournament second round match at the Caja Magica pavilion, in Madrid, Spain, 06 May 2015. EPA/ALBERTO MARTIN