Alexander Zverev, right, of Germany embraces Novak Djokovic of Serbia after Djokovic retired from 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 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)

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/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)

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)