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 semi-final 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 a 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 semi-finals 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 number two. "I mean, I'm playing Zverev, who is in great form, and he is going for his first Grand Slam. He's been close. I mean, I've seen him play. I practised with him as well here," he said."I think he loves the conditions. He's got a big serve. He's a super dangerous opponent on this surface against anyone."

Djokovic holds an 8-4 record over the 27-year-old and will be looking to new coach Andy Murray, who himself won three of his four meetings with Zverev, to establish a game plan.The Scot has been a calm and collected presence in Djokovic's courtside box during the tournament after the former rivals unexpectedly joined forces late last year.The Serbian, who is into a record 50th Grand Slam semi-final, headed straight over to embrace him after beating Alcaraz.

"I feel more and more connected with Andy every day. We face challenges every single day. People don't see that obviously," said Djokovic."We try to make the most out of every day and grow together. He's been as committed to my career and this tournament as he can be."So it was kind of a gesture of appreciation, respect for him, and the fact that he's out there, and he doesn't need to be. He accepted to work with me."He's giving all his support to me, to the whole team, and trying to make it work."This (against Alcaraz) was a huge win for all of us, including Andy and myself, you know, for the relationship. That's why I went to him, because I just felt very grateful that he's there."  

Ben Shelton will face defending champion Jannik Sinner 

Ben Shelton's Australian Open quarterfinal foe, Lorenzo Sonego, produced the shot of the tournament — diving to his left for a volley with so much spin that the ball bounced on one side of the net, then floated back over to the other — but it was the American who ended up with the victory Wednesday. The left-handed Shelton did some entertaining of his own, including earning cheers by doing a couple of push-ups after tumbling in the concluding tiebreaker, and he reached his second Grand Slam semifinal at age 22 by beating the unseeded Sonego 6-4, 7-5, 4-6, 7-6 (4).

“I'm relieved,” said Shelton, who will meet No. 1 Jannik Sinner of Italy on Friday for a spot in the final. “Shout out Lorenzo Sonego because that was some ridiculous tennis.” Sinner, the defending champion at Melbourne Park, completely overwhelmed the last Australian in the men's bracket, No. 8 Alex de Minaur, 6-3, 6-2, 6-1 at night. “It’s been too many times playing him and seeing the same thing. So I’m not even surprised anymore when I face him,” said de Minaur, who is now 0-10 against Sinner over their careers. “Matches like these happen.”

Sinner looked and played much better than he did — hand trembling, head dizzy — during a four-set struggle against Holger Rune in the fourth round. After giving himself a bit of a break on Tuesday, sleeping in and only hitting on court for about 30 or 40 minutes, Sinner said his body was much better.“For sure, was (my) best match of the tournament so far,” said Sinner, who stretched his unbeaten winning streak to 19 matches dating back to last season.

Shelton, who is seeded 21st, closed the first set against Sonego with a 144 mph (232 kph) ace, tied for the fastest serve over the past 1 1/2 weeks, and flexed his left arm after smacking a powerful forehand to close a 22-stroke point and earn a break in the second. His father Bryan, a former tour pro who is Ben's coach, grinned, too, while patting his own right biceps.A few points from the end, Shelton sprinted to get his racket on a seemingly unreachable ball, and fell into a courtside advertising board as Sonego hit an easy winner to take the point.Shelton stayed on the ground for a bit, then earned applause for his effort — and post-fall calisthenics.

When Shelton closed things with a 26th forehand winner — he had zero via backhands — he flexed again and sneered until his expression morphed into a smile.At his news conference, Shelton offered some unprompted comments critical of some of the people handling on-court post-match interviews.As good as Shelton is with his serves and forehands, his improving return game is a significant part of what carried him to the final four at the Australian Open for the first time.

He did just enough in that department, accumulating 11 break points and converting three, against Sonego, an Italian ranked 55th. Shelton entered the match coming through on 52% of his break chances, the highest rate among the eight men's quarterfinalists. Shelton lost to Novak Djokovic in the 2023 U.S. Open semifinals.

The other semifinal will be Djokovic vs. No. 2 Alexander Zverev. Djokovic continued his pursuit of an 11th Australian Open title, and unprecedented 25th major trophy, by overcoming a leg injury and Carlos Alcaraz 4-6, 6-4, 6-3, 6-4 in a quarterfinal that began Tuesday night and ended at nearly 1 a.m. on Wednesday.

The women's semifinals Thursday night are No. 1 Aryna Sabalenka, the tournament winner in each of the last two years, against No. 11 Paula Badosa, and No. 2 Iga Swiatek against No. 19 Madison Keys.