The Australian Open 2025: Jannik Sinner’s health a major talking point ahead of Alex De Minaur quarterfinal

Speculation continues to swirl around the health of World No.1 Jannik Sinner ahead of his hotly-anticipated quarterfinal clash with hometown hero Alex De Minaur tonight.

Sinner, who may have been suffering pneumonia, was filmed visibly shaking and in serious distress during his fourth round win over Holger Rune on Monday.

The two contenders battled on an intensely hot day before Sinner, who woke up unwell and skipped his usual pre-match warm-up, triumphed 6-3 3-6 6-3 6-2.

John Millman, a former Australian player, said he had not seen Sinner on the practice courts since Monday furthering fuelling the rumours the Italian, who has beaten de Minaur in all of their nine meetings, could be in doubt for tonight’s match.

“One thing I’ll say - and I’m no expert and maybe cameras picked up something else - but I didn’t see him at the courts yesterday,” Millman told the host broadcast on Wednesday morning.

“It was actually quite distressing (to watch against Rune) ... when you push your body beyond the limits you need more than a day to recover.

“I saw Alex, he was hitting. I didn’t see Jannik Sinner.”

But Lleyton Hewitt, who is part of De Minaur’s coaching team, poured cold water on any suggestion Sinner would not take to the court on Rod Laver Arena.

“Pretty sure he was on one of the indoor courts, in the gym on the NTC side,” Hewitt said.

“You’ve got to expect him (Sinner) to come out and go at 100 per cent right from the start.

“He was just having an average day a couple of days ago where he wasn’t feeling his best coming into the match but the big thing for Alex is he’s done the work.

“He knows he can last five sets and that’s what he has been training so hard for for so long but he’s up against it tonight.”

The Italian looked in serious physical distress in the first few games of the pivotal third set before leaving the court to receive treatment against Rune.

He returned a rejuvenated man as the temperature in Melbourne reached 33 degrees — and presumably higher in the closed confines of Rod Laver Arena.

Three games later Rune called his own timeout for treatment on his right leg, only for Sinner to hold to love in the following game to claim the third set.

Sinner has not made any public comments since the match about his fitness as he chases his second Australian Open title in as many years.

Meanwhile, one of tennis’s most respected analysts is convinced de Minaur can at last conquer Sinner and gatecrash the Australian Open semifinals.

De Minaur has lost the past seven matches against Sinner without even winning a set.

Australian strategist Craig O’Shannessy believes Sinner is more vulnerable right now - and not only because of the Italian’s ill health.

O’Shannessy, who helped Novak Djokovic to four grand slam titles while working with the Serb from 2017 to 2019, has noticed a sharp improvement in de Minaur’s attacking mindset and tactics.

“De Minaur’s got a couple of things in his favour,” O’Shannessy told AAP at Melbourne Park.

“Firstly, remember he got sick yesterday. I don’t know what it was but he certainly got the jitters.

“Number two is that Demon is winning 56 per cent of his baseline points, which is higher than Sinner, who’s at 55 per cent.

“It’s close but a one per cent advantage from the baseline is a big deal.

“So I see more offence. He looks more potent from the back of the court, making opponents uncomfortable.

“He’s rolling through the tournament with more confidence, and you just feel the tables have turned a bit.

“While Sinner was surging, it doesn’t feel like Sinner is surging at the moment.

“But it feels like Demon is surging.”

What makes O’Shannessy’s assessment and belief that de Minaur can spring a boilover even more telling is the fact the US-based coach and strategist has been one of the masterminds behind Italy’s rise from the tennis doldrums to super powers and back-to-back Davis Cup champions.

The 58-year-old has been working for the Italian federation since 2016 and plotted the game plans for Sinner and others during the past two Davis Cup finals, including their 2023 victory over de Minaur’s Australian team.

“With the way Sinner has been feeling, if he gets a gets a hot night, that would also help Demon,” O’Shannessy said.

“Humid conditions more than anything, if it’s not even hot, but if it’s really humid, and he continues attacking, he has a chance.

“He’s got to attack and that’s what he’s been doing well leading up to this match.

“So I think it does come down to baseline performance early in the point, but Demon is certainly peaking at the moment.

“Don’t get me wrong, de Minaur is still the underdog in this match-up but there’s a stronger feeling that he’s more ready than he’s ever been to take on the challenge.”

A victory over Sinner would present de Minaur with a huge opportunity to make the Open final.

He would play the winner of Wednesday’s other quarterfinal between American world No.20 Ben Shelton and unseeded Italian Lorenzo Sonego.

In Wednesday’s two women’s quarter-finals, American world No.14 Madison Keys plays resurgent Ukrainian Elina Svitolina before US eighth seed Emma Navarro takes on Polish world No.2 Iga Swiatek.

With 7NEWS and AAP