“If he cannot continue a tennis match, it really means he cannot continue a tennis match,” Zverev told spectators, stressing on the word “really”.

Moments earlier, Novak Djokovic had walked off Rod Laver Arena, a court on which he soaked in 10 times over adulation reserved for champions, to a ring of boos.

Djokovic had just clipped the wings of a potential marathon after the first turn that went on for an hour and 21 minutes and into a tiebreaker. At no point through those long minutes and rallies did Djokovic’s left leg, strapped after the injury from his previous match against Carlos Alcaraz, show any visible signs of stopping completely. And then, seemingly out of nowhere as he netted a simple volley facing set point at 5-6 in the tiebreaker, Djokovic walked up to Zverev and pulled the plug.

In the stands, fans gasped. On his chair, Zverev sat with the racquet pasted to his lips. A Djokovic mid-match retirement, after his younger days in the sport, has been a rare phenomenon (it hasn’t happened at the Australian Open since 2009, and in a Slam since the 2019 US Open). Of late, it’s getting a bit more common.

Djokovic said later it was a muscle tear. In his mind he hoped the extra rest day after the quarter-final, which he somehow managed to pull through, was going to be good enough to get him through the semi-final too. His 37-year-old body thought otherwise.

“Towards the end of that first set, I just started feeling more and more pain. It was too much to handle,” Djokovic said.

Two of the Serb’s last four Slam appearances have now ended in retirements. Djokovic was forced to withdraw from his 2024 French Open quarter-final because of a right knee injury from the previous round. Months later, he pulled out of the Paris Masters and the ATP Finals citing an unspecified injury. He turned up for the Australian Open well rested, only for the left leg to give in.

The man who was the epitome of fitness is now increasingly battling frailty. His tennis may still be doing quite a bit of talking, but his body is giving up more often. Worryingly for him, at the biggest of stages and deepest of settings. Rafael Nadal, Djokovic’s fierce rival, also went through this in the final chapters of his career (his last Wimbledon result was a semi-final walkover). Age does its thing even to the GOATs; whether it be to Nadal who was often injury-prone or Djokovic who has largely been a physical beast.

“The statistics are against me, in a way, in the last couple of years,” Djokovic said. “It’s not like I’m worrying approaching every Grand Slam now whether I’m going to get injured or not… (but) it is true that I’m getting injured quite a bit the last two years.”

Not that Djokovic was immune to injuries before. He’s had his fair share of forced physical pauses, yet not damaging enough to halt him mid-tournament going for titles at this frequency. Some of the 24-time Grand Slam champion’s most memorable triumphs have come while overcoming obstacles of the body. Only two years ago at the Australian Open, Djokovic went all the way without being able to practice between rounds — like he did not between Tuesday and Friday — and later revealed that he had a torn hamstring. In 2021 at the same Slam, he grappled with an abdominal issue while beating Zverev in the quarter-final firing over 20 aces and, again, winning the whole thing.

“Two years ago, I managed it better. On the court it (injury) didn’t bother me as much. This time that wasn’t the case,” Djokovic said.

Which, for Djokovic and his new coach Andy Murray, was a shame because the former felt as good on court over the past couple of weeks as he did in the last 12 months. He liked his chances, he said, “if I was physically fit and ready to battle”. There is a chance, he also said, that he may not be able to come back to his favourite Slam. That’s realising he is 37, even though he isn’t ready to give up.

“I’ll keep striving to win more Slams,” he said. “As long as I feel I want to put up with all of this, I’ll be around.”

At 37, Djokovic also realises the glaring threat to that. “Injury is the biggest enemy of a professional athlete.”