It took the double blow of illness and the oppressive conditions of a blistering Melbourne summer for Jannik Sinner to look uncomfortable on a hard, acrylic-based tennis court for the first time in well over a year. Throughout the 2024 season, Sinner not only held his opponents in a chokehold on the biggest stages, he had often done so with his typical calm, neutral expression barely changing. As Sinner methodically compiled significant titles throughout the 2024 season, he made his immense efforts appear to be routine.

Three sets into his highly anticipated intragenerational tussle with Holger Rune, though, Sinner was clearly uncomfortable. He limped gingerly between points, his hands shook as he sat down at the change of ends and, most importantly, his unforced errors piled up. Down two break points at 1-1 in set three, Sinner was in trouble.

At the sight of his opponent’s weakness, with a break point in hand, Rune did everything he could to grind Sinner to dust. He utterly refused to miss, pulling the Italian into a gruelling, lengthy exchange before attempting to take Sinner’s legs by dragging him forward to the net and back with a drop shot and lob. Somehow, even as each movement seemed more excruciating than the last, Sinner chased down every last ball and held on. Sinner closed out the delirious exchange on the 37th shot with a triumphant forehand drive volley winner before hunching over in exhaustion.

Sinner’s response to his most difficult moment of the tournament so far underlined his supreme mental fortitude as he successfully navigated a difficult, chaotic afternoon on Rod Laver Arena. Sinner returned to the quarter-finals in Melbourne with a 6-3, 3-6, 6-3, 6-2 win over the 13th-seeded Rune, keeping his Australian Open defence alive.

Afterwards, during his on-court interview, Sinner admitted that he was feeling so unwell in the morning that he did not warm up on-court for his match: “This morning was a very strange morning,” he said. “I didn’t even warm up today, trying to go on court as fit as I could. I knew in my mind before the match that I would struggle today.”

Sinner takes a moment to recover during his match on Rod Laver Arena. Photograph: Vincent Thian/AP

Sinner declined to expand on his physical condition during his post-match press conference but said he had been consulting with tournament doctors before his match. “I don’t want to talk so much how I felt today,” said Sinner. “I was not feeling really well. I think we saw that today, I was struggling physically. Came here as late as possible. I knew that it was going to be very, very difficult today – playing against a tough opponent, but also playing against myself a little bit.”

As Sinner and Rune lined up against each other for their fifth meeting, the series tied at 2-2, their respective seedings reflected their contrasting past year. Although he is 20 months younger than Sinner, Rune broke through first, spectacularly winning his first Masters 1000 title in 2022 at a time when Sinner was known for his mental frailty. While Sinner established himself as the best player in the world last year, Rune fell out of the top 10.

Their contrasting recent fortunes were reflected in a one-sided start for Sinner, but midway through the second set, he gradually became unstuck. The match reached a tipping point at 1-1 in the third set as Sinner faced two break points. He responded defiantly, dragging himself through the service game and gritting his teeth as he pumped his fist. At the change of ends, Sinner’s right hand shook violently as held up an ice towel to his face.

Rune plays a backhand during the last-16 clash. Photograph: Darrian Traynor/Getty Images

After holding serve for a 3-2 lead, Sinner received a medical timeout, a process that took just over 10 minutes. Sinner returned looking more comfortable and he gradually established control of the baseline with his suffocating depth, pace and weight of shot. He soon made his move, breaking serve for 5-3 in the set, a setback Rune responded to by calling for a medical timeout on his right thigh. The second injury break proved far less fruitful as Sinner easily closed out one of the most chaotic sets of the tournament.

Early in the fourth set, the match was interrupted once again as a netted serve from Sinner inadvertently broke the net, snapping the metal clip that is screwed into the ground in order to hold it in place. Play was suspended as an army of officials tried to fix the problem, a break that afforded Sinner more time to collect himself and close out an important win.

“It helped me,” said Sinner. “I was lucky today that [at] this point, 20 minutes off court, trying to get back physically, putting some cold water in my head, it was very helpful. It was big, big luck to me today.”