Novak Djokovic of Serbia plays a backhand return to Alexander Zverev of Germany during their semifinal match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Ng Han Guan)

Jannik Sinner of Italy receives medical treatment during his semifinal match against Ben Shelton of the U.S. at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Ng Han Guan)

Novak Djokovic of Serbia reacts during his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia reacts at a press conference after retiring in his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Alexander Zverev, right, of Germany embraces Novak Djokovic of Serbia after Djokovic retired in their semifinal match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia shakes hands with chair umpire James Keothavong after retiring from his semifinal against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia looks to his coaches box during his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Manish Swarup)

Alexander Zverev of Germany reacts after winning the first set in his semifinal match against Novak Djokovic of Serbia at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia plays a forehand return to Alexander Zverev of Germany during their semifinal match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Ng Han Guan)

Novak Djokovic of Serbia reacts during his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Manish Swarup)

Jannik Sinner of Italy celebrates after defeating Ben Shelton of the U.S. in their semifinal match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Ng Han Guan)

Novak Djokovic of Serbia gestures as he leaves Rod Laver Arena after retiring in his semifinal match against against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia wipes the sweat from his face during his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Asanka Brendon Ratnayake)

Jannik Sinner of Italy reacts as Ben Shelton of the U.S. leaves Rod Laver Arena following their semifinal match at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Vincent Thian)

Novak Djokovic of Serbia gestures as he leaves Rod Laver Arena after retiring in his semifinal match against against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025.(AP Photo/Asanka Brendon Ratnayake)

Novak Djokovic of Serbia shakes hands with chair umpire James Keothavong after retiring from his semifinal match against Alexander Zverev of Germany at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Ng Han Guan)

Ben Shelton of the U.S. gestures as he leaves Rod Laver Arena following his semifinal match against Jannik Sinner of Italy at the Australian Open tennis championship in Melbourne, Australia, Friday, Jan. 24, 2025. (AP Photo/Vincent Thian)