Jannik Sinner at the Australian Open — Jannik Sinner grimaces

Jannik Sinner is still on course to retain his Australian Open title, but he has suffered physically in the first four rounds.

There’s been a lot of talk on tennis schedules pushing the modern player to the limits. In 2025, just under five per cent of ATP matches ended with the withdrawal of one competitor. Carlos Alcaraz claimed that “they are trying to kill us in some way” when discussing the ever-increasing calendar in 2024.

Sinner has kept his counsel on the matter, taking a more “it is what it is” approach, although he has been at the forefront in the call for better player compensation and welfare from the Slams.

And yet the Italian has looked as vulnerable to hot conditions as anyone in recent times. On Saturday, his chances of retaining the Melbourne crown were teetering. Alcaraz thinks he has an edge. He could be right.

The world No 2’s body was failing against Eliot Spizzirri due to the sweltering temperature on Rod Laver Arena. The heat stress rule saved Sinner when he was cramping badly, giving him a ten-minute lifeline to recover from a break down in the third set as the roof was closed. “I got lucky”, said the four-time Slam winner.

The current champion also had his struggles in last year’s run to the title in the last 16 encounter against Holger Rune, eventually recovering from a medical timeout to win in four. “I knew in my mind I would struggle today,” he admitted.

When Daniil Medvedev called the Melbourne conditions “brutal”, he was speaking for most. Gael Monfils felt like he was “dying on the court” back in 2018.

But Sinner’s back catalogue of matches has a familiar bugbear running through them. He was similarly cramped against Tallon Griekspoor at Shanghai, although the 80 per cent humidity was something that would drain the life out of most at the back end of the season. This time, the Italian had to retire and was helped off the court.

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Sinner looked visibly unwell in his last eight clash with Daniil Medvedev at Wimbledon 2024, contributing to a five-set defeat. In the Cincinnati final this August, he fell 5-0 down in 23 minutes to Alcaraz and pulled out with the US Open just around the corner.

Sinner has shown time and time again the requisite fight that all great champions possess. On the verge of defeat in the miraculous five-and-a-half-hour French Open showpiece, the eventual runner-up came back from a dead man walking to prolong the match to a Championship tiebreak. It was a good advert for pickle juice and a survivor’s instinct.

When Sinner was trying to push through his Next Gen graduation, he suffered significantly from retirements and withdrawals. These growing pains were a concern. L’Equipe summed it up well: “Jannik Sinner is fantastic. But he started the year in the top ten and is considered the young man who could win it all. It certainly seems like a physiological step to adapt to the new needs without forgetting that Sinner has not been spared from some physical defects.”

Those physical defects included withdrawing against Nick Kyrgios at Indian Wells in 2022 through illness, pulling out after five games of a Miami Open quarter-final with Francisco Cerundolo weeks later because of blisters, and retiring from a fourth-round clash at Roland Garros against Andrey Rublev that spring with a knee issue.

These things happen. Alcaraz has pulled out of tournaments to protect himself, but he’s not as prone to the health dips that have afflicted his great rival.

Sinner’s five-set record is 6-10 compared to Alcaraz’s almost perfect 14-1. He hasn’t won a match that has extended beyond three hours and fifty minutes. Not many can push him that far.

Even in the midst of winning eight titles in 2024, former fitness coach Marco Panichi mentioned that one area to improve was “physically lasting longer” so that Sinner could engage in a “high cruising speed” to more effect. It’s still a work in progress.

In a tournament that is testing the human condition to the limit, longevity will be the difference should Sinner make it to Sunday. It will be about the stamina as well as the stunning shots on February 1.

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Does Jannik Sinner struggle too much in the heat of battle?