Greek star Stefanos Tsitsipas is a step closer to a breakthrough grand slam title after surviving a huge comeback from Jannik Sinner to advance to the Australian Open quarter-finals with a "ripper" win.

A semi-finalist at Melbourne Park in his last two appearances, third seed Tsitsipas looked to be cruising against Sinner when he claimed the first two sets on Sunday night.

But the Italian, who recovered to win from two sets down for the first time in his third-round triumph over Marton Fucsovics, wasn't going to lie down.

He levelled the match at two sets all before Tsitsipas improved his serve and steadied to win the four-hour battle 6-4 6-4 3-6 4-6 6-3 at Rod Laver Arena.

"It was a long match. I felt like I spent an entire century on this court playing tennis," a relieved Tsitsipas said.

"It felt so long, I mean, what a great night. That was superb, a 'ripper' as they say here."

Known for taking tactical toilet breaks, Tsitsipas headed down the tunnel after dropping the third set.

It failed to halt Sinner's momentum but an adjustment to the Greek's serve in the fifth set turned the tide back his way.

Tsitsipas landed 92 per cent of first serves in the fifth set and won 79 per cent of those points.

"I had an unbelievable opponent on the other side of the court today playing incredible tennis in the third and fourth sets," Tsitsipas said.

"I stayed really calm ... I released my arm a little bit, released my wrist on the serve, and I think that helped me a lot to generate more power and accuracy.

"It's something that I wasn't doing before and it completely changed the way I approached this match since that moment when I did this minor adjustment.

"That helped me serve it out pretty well towards the end without being too tense.

"I'm happy I figured it out."

Tsitsipas has only lost one match after winning the first two sets. That was in his only grand slam final appearance - the 2021 French Open decider against Novak Djokovic.

The 24-year-old next meets unseeded Czech Jiri Lehecka, who has never previously been past the first round at a grand slam.

But Tsitsipas will be wary of the world No.71, who has already toppled three seeds on his path to the last eight.

― With AAP.