Australian Open: Injured Novak Djokovic booed after withdrawing, setting up final between Alexander Zverev and defending champion Jannik Sinner

In a stunning development at the Australian Open, Novak Djokovic withdrew because of injury after losing the first set of his semifinal match versus Alexander Zverev.

Zverev, the No. 2 seed, won a grueling first set in a 7–6 tiebreaker that lasted one hour and 26 minutes. No. 7 Djokovic decided he couldn't continue with a left leg injury that was hindering him throughout the match. The 10-time Australian Open champion revealed afterward that the injury was a muscle tear.

Zverev will face defending Australian Open champion and No. 1 seed Jannik Sinner, who beat American Ben Shelton 7-6 (2), 6-2, 6-2, in Sunday's final. Zverev is pursuing his first major tournament title.

In the first semifinal, Djokovic put his thumb up and conceded the match as soon as the first set ended. Zverev looked shocked and the very pro-Djoker crowd at Rod Laver Arena was initially hushed in disbelief before some fans started booing.

Djokovic responded to the boos by flashing two thumbs up to the crowd.

Djokovic set the pace early in the match and appeared to be controlling play, to Zverev's frustration. Despite being able to return serve consistently, Zverev was often stymied by Djokovic's play at the net.

Though the injury bothered Djokovic during his quarterfinal victory over Carlos Alcaraz and he wasn't able to practice on Wednesday or Thursday before the match with Zverev, it didn't appear to be an issue in the early going against Zverev. During the ESPN telecast, broadcasters John McEnroe and Jim Courier both remarked that Djokovic wasn't playing like he was injured.

That obviously changed as the first set progressed. Djokovic was limping as he went to his chair at the change of ends. Yet he still almost won the first set. What would have happened had Djokovic won? Would he have attempted to play another set or two? He admitted that would have been difficult.

For Djokovic, his retirement from the match means that he won't win his record 25th major title and 11th Australian Open. Injuries have prevented him from finishing two of his past four Grand Slam tournaments. He withdrew from last year's French Open before the quarterfinals due to a torn meniscus in his right knee.

Asked if this could be his final Australian Open, the soon-to-be 38-year-old Djokovic said, "There is a chance, who knows."

In the second semifinal, Sinner cruised past Shelton after a tough first set went to tiebreak. Sinner, a 23-year-old from Italy, is looking for his second straight Aussie crown and third major overall. He also won the 2024 US Open after being cleared in a doping case. The World Anti-Doping Agency is still seeking a one-year suspension of Sinner after the International Tennis Integrity Agency ruled the steroid found in Sinner's test was the result of accidental contamination. A hearing for the appeal is scheduled for April.

Against Shelton, Sinner briefly needed treatment from a trainer in the third set after he grabbed his right leg. He said afterward he was suffering from cramps.

Zverev will be in his third major final after losing each of his first two attempts at a title in five sets.