Beaten opponent reveals truth after Jannik Sinner caught in storm over mid-match move at Aus Open

World No.1 Jannik Sinner has copped some backlash for his mid-match Medical Time Out against Holger Rune as he prepares to play Alex de Minaur in the quarter-final of the Australian Open. Sinner was visibly struggling in the second and third set against Rune with his hands were visibly shaking between games in the Australian heat.

Sinner's player's box urged the Italian to take a MTO in the third set having just held serve for a 3-2 lead. The 23-year-old agreed and left the hot conditions on Rod Laver Arena. The Italian appeared around 10 minutes off court, which raised eyebrows wth many feeling he was allowed preferential treatment during an extended break.

After a short break, Sinner returned and appeared rejuvenated having put it back on Rune immediately. This surprised the young Danish star. Sinner regathered his momentum and appeared to be hitting his forehand with more vigour after the short break.

Sinner broke Rune and was serving for the set at 5-4 when the Danish star took his own time out to see the physio. This prompted a wry smile from Sinner having his momentum halted in similar fashion. Rune was never able to recover having gone down in four sets 6-3, 3-6, 6-3, 6-2.

While Rune was sympathetic for Sinner, who was visibly struggling at the change of ends, he did have an issue with the time it took for the Italian to come back on court. The timing of the MTO from the Italian also frustrated Rune who claimed he had the momentum after taking the second set.

“It’s perfectly fine that you get checked, it was a very warm day today even though there was not sun all the time - it was very humid. I was also feeling it,” Rune said. “Definitely it’s fair that he got checked (but) I think it took longer than I expected. It was around 10 minutes, maybe even more, so that was a bit brutal in the middle of the set. But it is what it is.

“I had good momentum in this moment so it was not the worst timing from his side ... he came back firing, so I don’t know what they did.”

Jannik Sinner defends MTO in fourth round victory

Most tennis experts agreed Sinner did the right think listening to his team's advice and seeking help off the court during a break. "I was a bit concerned for him (Sinner) when I was watching it on the television," Aussie John Millman said on Channel 9.

"We found out later he is actually suffering from an illness and it was quite distressing. He was ginger on his feet. His arms were shaking when he was trying to take in water. This knocks you around. Make no mistake. He will be feeling this today."

And the Italian admitted he was dizzy and needed to fight through the pain. “I don’t want to talk so much about how I felt today. I was not feeling really well,” Sinner added when quizzed on his condition.

“I was struggling physically and I came here as late as possible as I knew that it was going to be very, very difficult, playing against a tough opponent but also playing against myself a little bit. I was a bit dizzy at times.”

Jannik Sinner to meet Alex de Minaur in the quarter-final

Sinner will now play de Minaur in the quarter-final of the Australian Open. De Minaur has never defeated the Italian in nine attempts, but would have been hoping to play the World No.1 in hot and humid conditions.

The Aussie revelled in the hot conditions in his second round victory against Francisco Cerundolo as the Argentinian struggled with cramp. De Minaur even wrote "bring the Aussie heat" on the camera lens after the match and spoke about his love of those conditions.

However, this might come to fruition for the Aussie. Much cooler conditions are expected in Melbourne for the quarter-final showdown with Sinner. This should favour the Italian when they play at night on Rod Laver Arena.