Serbia's Novak Djokovic celebrates as he won the quarterfinal match of the French Tennis Open against Germany's Alexander Zverev at the Roland-Garros stadium in Paris.

Winner Serbia's Novak Djokovic, right, and Germany's Alexander Zverev hug after their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Serbia's Novak Djokovic slides for the ball against Germany's Alexander Zverev during a quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Germany's Alexander Zverev plays a shot against Serbia's Novak Djokovic during their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Serbia's Novak Djokovic reacts after winning advantage in the last game of his match-winning set during a quarterfinal match against Germany's Alexander Zverev during the French Tennis Open at the Roland-Garros stadium in Paris.

Spectators watch the quarterfinal match of the French Tennis Open between Germany's Alexander Zverev and Serbia's Novak Djokovic at the Roland-Garros stadium in Paris.

Germany's Alexander Zverev serves against Serbia's Novak Djokovic during their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Serbia's Novak Djokovic plays a shot against Germany's Alexander Zverev during their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Germany's Alexander Zverev plays a shot against Serbia's Novak Djokovic during their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.

Serbia's Novak Djokovic plays a shot against Germany's Alexander Zverev during their quarterfinal match of the French Tennis Open at the Roland-Garros stadium in Paris.