Czech Republic’s Barbora Strycova returns the ball to Madison Keys of the USA during their second round match of the Mutua Madrid Open tennis tournament at the Caja Magica court in Madrid, Spain, 02 May 2016. EPA/JUANJO MARTIN

Argentina’s Leonardo Mayer in action against Spanish Feliciano Lopez during their first round match of the Mutua Madrid Open tennis tournament at the Caja Magica court in Madrid, Spain, 02 May 2016. The Mutua Madrid Open runs from 29 April to 08 May. EPA/CHEMA MOYA

Madison Keys of the USA returns the ball to Czech Republic’s Barbora Strycova during their second round match of the Mutua Madrid Open tennis tournament at the Caja Magica court in Madrid, Spain, 02 May 2016. EPA/JUANJO MARTIN

Gilles Simone of France in action against Marcos Baghdatis of Cyprus during their first round match of the Mutua Madrid Open tennis tournament at the Caja Magica court in Madrid, Spain, 02 May 2016. The Mutua Madrid Open runs from 29 April to 08 May. EPA/CHEMA MOYA

Victoria Azarenka of Belarus returns the ball to Britain’s Laura Robson during their first round match of the Mutua Madrid Open tennis tournament at the Caja Magica court in Madrid, Spain, 01 May 2016. EPA/JUANJO MARTIN