Serbia's Novak Djokovic celebrates beating Mackenzie McDonald of the U.S. after their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic returns the ball to Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic returns the ball to Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic serves against Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Mackenzie McDonald of the U.S. returns the ball to Serbia's Novak Djokovic during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Mackenzie McDonald of the U.S. returns the ball to Serbia's Novak Djokovic during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Mackenzie McDonald of the U.S. returns the ball to Serbia's Novak Djokovic during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic talks with officials as he plays Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic returns the ball to Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.

Serbia's Novak Djokovic returns the ball to Mackenzie McDonald of the U.S. during their first round match of the French Tennis Open, at the Roland-Garros stadium, in Paris.