Australian Open: Novak Djokovic quits semi-final due to torn muscle in left leg after one set versus Alexander Zverev

Novak Djokovic said "there is a chance" he has played in his last Australian Open after retiring hurt and being booed off in his semi-final against Alexander Zverev.

Djokovic withdrew from the final-four clash after losing the opening set in a tie-breaker 7-5, due to a torn muscle in his left leg, leaving Rod Laver Arena to a chorus of boos.

There had been doubt about the record 24-time Grand Slam champion's fitness after he initially suffered the injury during his four-set quarter-final triumph over Carlos Alcaraz which ran late on Tuesday night.

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"I did everything I possibly can to manage the muscle tear that I had," Djokovic told reporters after his semi-final retirement.

"Medications, the strap and the physio work helped to some extent today. But towards the end of that first set I just started feeling more and more pain.

"It was too much to handle for me at the moment. Unfortunate ending, but I tried.

"Even if I won the first set, it's going to be a huge uphill battle for me to stay physically fit enough to stay with him in the rallies for another... two, three, four hours. I don't think I had that, unfortunately, today in the tank."

Quizzed on whether that might be his final appearance at Melbourne Park, the 37-year-old said. "I don't know. There is a chance. Who knows? I'll just have to see how the season goes.

"I want to keep going. But whether I'm going to have a revised schedule or not for the next year, I'm not sure."

A 10-time champion in Australia, Djokovic added: "I normally like to come to Australia to play. I've had the biggest success in my career here. So if I'm fit, healthy, motivated, I don't see a reason why I wouldn't come.

"But there's always a chance [it is the last time]."

Djokovic again stressed his eagerness to continue playing, but admitted his body is becoming more injury prone. This is the second time in the last four Grand Slams that he has been forced to pull out, having suffered a knee injury during the French Open.

"It's not like I'm worrying approaching every Grand Slam now whether I'm going to get injured or not, but statistics are against me in a way in the last couple of years," he said.

"I want to keep going. I'll keep striving to win more Slams. And, as long as I feel that I want to put up with all of this, I'll be around."

Zverev to face Sinner in men's final

Djokovic had heavy strapping on his thigh for the match but appeared to be moving well during the early exchanges of an opening set that ended up going the distance and lasting one hour and 21 minutes.

Both men had chances to break, with Zverev unable to take five break points across two separate Djokovic service games and the German recovering from 0-40 down on serve in the fourth game of the set.

It was tight in the tie-break too until Djokovic netted an easy volley at 5-6 to hand Zverev the set, the Serb almost immediately shaking hands with his opponent afterwards.

In the second men's semi-final, defending champion and world No 1 Jannik Sinner sailed through to another final after seeing off big-serving American Ben Shelton in straight sets, 7-6 (7-2) 6-2 6-2.

Shelton, appearing in his first Australian Open semi-final and just his second at Grand Slam level, forced two set points in the first but critically fell short before losing out in a tie-break in which Sinner streaked into a 5-0 lead.

With that missed opportunity clearly still on his mind, Shelton was broken immediately to start the second set, one he'd lose without much resistance.

The third proved far more competitive, with Shelton back to pushing Sinner all the way, but at 2-2 it was Sinner who struck for the first break after Shelton missed out on three break point chances across the Italian's previous two service games.

From there, Sinner proved composed and professional to close out the match and book a final meeting with Zverev on Sunday.

Zverev urges crowd not to boo Djokovic

Zverev, who is through to his third Grand Slam final - chasing a first title - was quick to leap to the booed Djokovic's defence in his on-court interview, saying: "The very first thing I want to say is please don't boo a player when he goes out injured.

"I know that everybody paid for tickets but Novak Djokovic is somebody that has given this sport for the past 20 years absolutely everything of his life.

"He has won this tournament with an abdominal tear, won this tournament with a hamstring tear; if he feels he can't continue a tennis match, he can't continue a tennis match."

Zverev did, however, admit he too was surprised to see Djokovic throw in the towel, adding: "I thought it was quite a high-level first set.

"Of course, the longer you continue, the worse it can get and maybe he was not moving as well in the tie-break.

"I'm happy to be in the final of the Australian Open but, on the other hand, there's no guy on the tour that I respect more than Novak.

"Whenever I've struggled, I could call him, ask him for advice. I wanted it to be a tough five-set match as well."

Djokovic: I'll chat to Murray about the next step

Djokovic's withdrawal means a premature end to his first tournament with coach Andy Murray, and it remains to be seen whether the arrangement will continue.

"We both were disappointed with what just happened, so we didn't talk about the future steps," Djokovic said on the situation.

"I'll definitely have a chat with Andy and thank him for being here with me, give him my feedback, which is, of course, positive, see how he feels and we make the next step."