Serbia's Novak Djokovic returns the ball to France's Jo-Wilfried Tsonga during their fourth round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Sunday, June 1, 2014. (AP Photo/David Vincent)
Canada's Eugenie Bouchard serves the ball during the fourth round match of the French Open tennis tournament against Germany's Angelique Kerber at the Roland Garros stadium, in Paris, France, Sunday, June 1, 2014. (AP Photo/Michel Euler)
Switzerland's Roger Federer looks down as he plays Latvia's Ernests Gulbis during their fourth round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Sunday, June 1, 2014. (AP Photo/David Vincent)
Latvia's Ernests Gulbis waves after defeating Switzerland's Roger Federer during their fourth round match of the French Open tennis tournament at the Roland Garros stadium, in Paris, France, Sunday, June 1, 2014. (AP Photo/David Vincent)