Novak Djokovic of Serbia celebrates his victory after the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States serves during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia celebrates his victory after the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States serves during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Novak Djokovic of Serbia reacts during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)

Aleksandar Kovacevic of the United States returns the ball during the men's singles first round match between Novak Djokovic of Serbia and Aleksandar Kovacevic of the United States at the French Open tennis tournament at Roland Garros in Paris, France, on May 29, 2023. (Xinhua/Gao Jing)