Alexander Zverev is through to his first Australian Open final after Novak Djokovic suddenly withdrew from their semifinal match.

Zverev, the second seed at Melbourne Park, had just won a tense tiebreak to win the opening set 7-6 (5) in one hour and 21 minutes on Friday afternoon when Djokovic withdrew from the match.

Alexander Zverev(L) comforts Novak Djokovic after the men's singles semifinals between Novak Djokovic of Serbia and Alexander Zverev of Germany at Australian Open tennis tournament in Melbourne, Australia, Jan. 24, 2025. (Xinhua/Ma Ping)

It means that the 27-year-old German will play for his first Grand Slam title in Sunday night's final against either world No. 1 and defending champion Jannik Sinner or the 21st-seeded U.S. player Ben Shelton.

Djokovic suddenly quit from the match because of a torn muscle in his left leg.

"Towards the end of the first set I just started feeling more and more pain," Djokovic told reporters at a news conference. "Unfortunate ending, but I tried."

Asked if there would be any chance that he would continue if he had won the first set, Djokovic said maybe he would try a little bit longer.

"If I won the first set, maybe I would try, yeah, I don't know, a few more games, half a set, maybe a set. I don't know," he said. "It was getting worse and worse."

Zverev said that there is nobody on the tour he respects more than Djokovic.

"He has won this tournament with an abdominal tear, he has won this tournament with a hamstring tear, if he cannot continue a tennis match, it really means he cannot continue a tennis match," he said.

Djokovic, who was seeking his 25th Grand Slam title and 100th career title at the Australian Open, had shown no sign of being inhibited by the leg injury for which he received medical treatment during his quarterfinal victory over Carlos Alcaraz.

However, Zverev said he did see the 37-year-old "struggle a bit more" during the tiebreak.

The first 11 points of the tiebreak had gone to serve, giving Zverev his first set point when Djokovic hit a routine volley into the net. As Zverev approached his bench, Djokovic notified the umpire of his withdrawal and shook hands with a visibly stunned Zverev.

Djokovic made only 54 percent of his first serves and hit 11 winners and 16 unforced errors in the set, but had managed to save five break points to force the tiebreak.

His best shot in the match came at 4-4 in the tiebreak with a perfect lob sailing over the outstretched racquet of Zverev at the net and dropping onto the baseline. It would prove to be the final point won by Djokovic.

Zverev has previously played in two Grand Slam finals - at the 2020 US Open and 2024 French Open - losing both in five sets.

"It would be nice to win one more set than the first two I've played," he said. "I feel like maybe it's time for me to have some luck in a Grand Slam final."

Sinner and Shelton will play their semifinal on Friday night.