Sinner toughs it out through illness to reach last eight

Defending champion and top seed Jannik Sinner overcame a debilitating medical episode as well as Dane Holger Rune to reach the quarter-finals of the Australian Open for the third time with a 6-3 3-6 6-3 6-2 victory on Monday.

The world number one had looked like continuing his serene progress through the draw when he wrapped up the opening set after 33 minutes on the back of two breaks of serve.

The 23-year-old started to struggle physically early in the second set, however, and appeared even weaker after stretching in vain for one return.

"Today was a strange morning, I didn't even warm up...I knew in my mind that I would struggle today," Sinner said.

"It was for sure, very, very tough, I knew he had some very long matches before this one so I tried to stay there mentally. I just tried to stay connected with my service game and then on the returning game, just trying to see what happens."

Rune was not going to look a gift horse in the mouth and moved his opponent around the court as much as possible, the 13th seed converting his first break point of the match when Sinner double-faulted and serving out to clinch the second set.

Sinner, his hand shaking as he mopped his face with a towel, went to the locker room before the third set and fended off two break points in the third game, the second after a breathtaking 37-shot point which he won with a crosscourt winner.

The Italian slumped over his racket as the crowd gave the players a huge ovation, however, and a couple of games later he called for a doctor and went off court for a medical timeout.

Rune, looking to became the first Danish man to reach the quarter-finals at Melbourne Park, was struggling to make his physical advantage tell and Sinner, now moving more freely, broke for 5-3 before serving out to claim the third set.

It was now Rune's turn for a trip to the locker room, and a 20-minute delay while the net anchor was fixed allowed for more recovery time, welcome also for the Dane who played five, four and five sets in his first three matches.

Sinner pounced to break for 2-1 in the fourth set on the back of three Rune errors and, with his serve back at full power, his 18th successive win at tour level looked assured.

A 54th unforced error from Rune secured Sinner's passage to the last eight of a Grand Slam for a 10th time, equalling the Italian record set by Nicky Pietrangeli in the 1950s and 1960s.

Sinner will next face either local hopeful Alex de Minaur or American young gun Alex Michelsen, who he has played a combined 11 times winning them all.