US Jack Sock returns the ball to Bulgaria's Grigor Dimitrov during the men's first round at the Roland Garros 2015 French Tennis Open in Paris on May 26, 2015. AFP PHOTO / MIGUEL MEDINA (Photo credit should read MIGUEL MEDINA/AFP/Getty Images)
US Jack Sock returns the ball to Bulgaria's Grigor Dimitrov during the men's first round at the Roland Garros 2015 French Tennis Open in Paris on May 26, 2015. AFP PHOTO / MIGUEL MEDINA (Photo credit should read MIGUEL MEDINA/AFP/Getty Images)