MELBOURNE — Novak Djokovic feels as mentally and emotionally motivated as he's ever been, but the Serbian great admits to be being worried about his creaking body ahead of an Australian Open semifinal with "super dangerous "Alexander Zverev.

The irrepressible 37-year-old put to bed any doubts about his ability to add to his 24 Grand Slam titles with a scintillating four-set takedown of Carlos Alcaraz in the Melbourne last eight on Tuesday.

But while the 10-time Australian champion was able to pull out every trick in the book to get past a man 16 years his junior, it took its toll.

He had to leave court for a medical timeout at 4-5 in the first set, returning with his upper left leg taped and on painkillers to battle through.

Asked whether it was a hamstring or groin problem, he did not want to elaborate, but said: "It's very similar to what I had few years ago, 2023, to be exact."

Djokovic famously won the 2023 Australian Open while managing an injury in the same area.

"I'll take it day by day. Now it's really about recovery," he added.

"I'm concerned. I am, to be honest, physically. But if I manage somehow to be physically good enough, I think mentally, emotionally I'm as motivated as I can be."

Zverev is into the semifinals for a second straight year and is laser focused on finally winning a maiden Slam title after a decade of trying.

Last year at the same stage he crashed to Daniil Medvedev in five sets after holding a 2-0 lead and is understandably wary of Djokovic, even if he is carrying an injury.

"I'm going to prepare myself for a tough battle," he said. "I'm going to prepare myself for a very intense and high-level match."

Djokovic is equally cautious about the German, who is at a career-high world No 2.

"I mean, I'm playing Zverev, who is in a great form, and he is going for his first Grand Slam. He's been close. I mean, I've seen him play. I practiced with him as well here," he said.

"I think he loves the conditions. He's got big serve. He's a super dangerous opponent on this surface against anyone."