Sinner fires up in the heat to reach Australian Open quarter-finals

Jannik Sinner swept aside concerns about his heat tolerance as he breezed to a 6-1 6-3 7-6(2) win over fellow Italian Luciano Darderi on Monday to reach his fourth Australian Open quarter-finals.

With the temperature rising to 33 degrees Celsius in the evening match at Margaret Court Arena, all eyes were on the defending champion following his dramatic cramping in the third round on a scorching day against American Eliot Spizzirri.

But there were no signs of trouble on Monday as Sinner ran full pelt from start to finish against 22nd seed Darderi, keeping court-time to a comfortable two hours and nine minutes.

"It was very, very difficult, first of all. We are very good friends off the court.

"I got very, very tired (in the third set) so I'm very happy I closed it in three sets."

While unseeded Spizzirri gave Sinner a scare with his tenacity and firepower, Argentine-born Darderi made the champion's job far easier by not turning up in the first two sets.

Sinner stormed to a 5-0 lead in the first before Darderi, in his first appearance in the last 16 of a Grand Slam, finally held serve.

Sinner responded by serving out to love, wrapping up the set in 27 minutes with his 12th winner, a monstrous crosscourt forehand that kissed the sideline.

Struggling to stay in touch, Darderi completely lost his rag in the third game, and slammed his racket into the court when he slapped a loose backhand well over the baseline.

He fired a forehand wide to be broken on the next point and smashed a tennis ball high into the crowd to earn a code of conduct warning.

Though able to simmer down and hold serve a couple of times, Darderi double-faulted twice in succession to gift the second set and slumped in his chair to have a trainer work on a problematic left thigh.

Darderi dug deep, though, to make a game of the third set and gradually made inroads by attacking Sinner's forehand.

Sinner faced four break points at 4-4 but saved them all and returned the pressure on Darderi's serve.

Darderi saved two match points to delight the centre court crowd but it was a brief stay of execution as Sinner charged to a 6-2 lead in the tiebreak before closing it out when Darderi hit long.

Sinner will meet Ben Shelton or Casper Ruud for a place in the semi-finals.