Japanese tennis player Kei Nishikori in action against Spanish Roberto Bautista during their Madrid Open tennis tournament fourth round match played at Caja Magica Pavilion, in Madrid, Spain, 07 May 2015. EPA/JUANJO MARTIN

Czech Republic’s Tomas Berdych returns the ball to France’s Jo-Wilfried Tsonga during their third round match of the Mutua Madrid Open tennis tournament at the Caja Magica tennis complex in Madrid, Spain, 07 May 2015. EPA/CHEMA MOYA

Denmark’s Caroline Wozniacki returns the ball to Russia’s Maria Sharapova during their quarter final match of the Mutua Madrid Open tennis tournament at the Caja Magica tennis complex in Madrid, Spain, 07 May 2015. EPA/CHEMA MOYA

Bulgaria’s Grigor Dimitrov returns the ball to Swiss Stanislas Wawrinka during their third round match of the Mutua Madrid Open tennis tournament at the Caja Magica tennis complex in Madrid, Spain, 07 May 2015. EPA/CHEMA MOYA

Spain’s Rafael Nadal reacts during his third round match against Italy’s Simone Bolelli at the Mutua Madrid Open tennis tournament at the Caja Magica tennis complex in Madrid, Spain, 07 May 2015. EPA/JUANJO MARTIN

British tennis player Andy Murray celebrates his victory 6-2 and 6-0 over Spanish Marcel Granollers during their Madrid Open tennis tournament round of 16 match at Caja Magica Pavilion, in Madrid, Spain, 07 May 2015. EPA/ALBERTO MARTIN