Switzerland's Roger Federer serves the ball during the first round match of the French Open tennis tournament against Slovakia's Lukas Lacko at the Roland Garros stadium, in Paris, France, Sunday, May 25, 2014. (AP Photo/Darko Vojinovic)
Switzerland's Belinda Bencic returns the ball during the first round match of the French Open tennis tournament against Venus Williams of the US at the Roland Garros stadium, in Paris, France, Sunday, May 25, 2014. (AP Photo/David Vincent)
Venus Williams of the US returns the ball during the first round match of the French Open tennis tournament against Switzerland's Belinda Bencic at the Roland Garros stadium, in Paris, France, Sunday, May 25, 2014. (AP Photo/David Vincent)
Switzerland's Roger Federer wipes his face during the first round match of the French Open tennis tournament against Slovakia's Lukas Lacko at the Roland Garros stadium, in Paris, France, Sunday, May 25, 2014. (AP Photo/Darko Vojinovic)
Switzerland's Roger Federer returns the ball during the first round match of the French Open tennis tournament against Slovakia's Lukas Lacko at the Roland Garros stadium, in Paris, France, Sunday, May 25, 2014. (AP Photo/Darko Vojinovic)