A ball boy waits for his turn as Serena Williams of the USA plays against Victoria Azarenka of Belarus during their third round match for the French Open tennis tournament at Roland Garros in Paris, France, 30 May 2015. EPA/ROBERT GHEMENT

Ana Ivanovic of Serbia during a break during her match against Ekaterina Makarova of Russia at their fourth round match for the French Open tennis tournament at Roland Garros in Paris, France, 31 May 2015. EPA/ROBERT GHEMENT

Ball children wait for their turn during the first round match of Christian Lindell of Sweden in action against Jo-Wilfried Tsonga for the French Open tennis tournament at Roland Garros in Paris, France, 24 May 2015. EPA/ETIENNE LAURENT

Ball children rest during the French Open tennis tournament at Roland Garros in Paris, France, 29 May 2015. EPA/ETIENNE LAURENT

A ball girl collects balls as Richard Gasquet of France plays against Kevin Anderson of South Africa during their third round match for the French Open tennis tournament at Roland Garros in Paris, France, 30 May 2015. EPA/ROBERT GHEMENT