Jannik Sinner has hauled himself back from the brink of elimination to reach the Australian Open second week and keep his hopes of a breakthrough grand slam alive.

The Italian is the first man through to the fourth round after pulling off a stunning five-set comeback against Hungarian Marton Fucsovics, prevailing 4-6 4-6 6-1 6-2 6-0.

In the process, he teed up a blockbuster clash with No.3 seed Stefanos Tsitsipas of Greece, who eased past Dutchman Tallon Griekspoor in straight sets shortly after, winning 6-2 7-6 (7-5) 6-3.

Sinner was in dire straights after dropping the opening two sets.

But his predicament spurred the 21-year-old, who has Australian super coach Darren Cahill in his team, into action as he reeled off the first five games of the third set and dropped just three games in total across the final three sets.

"For sure the first two sets were very tough for me," Sinner said.

"Obviously I had to change something in my game after the two sets.

"I was feeling the ball quite well also in the beginning but the final shots I was missing a little bit, also tactically I was not so good.

"Obviously made a lot of work in the off-season especially physically and today I was good physically also in the last set.

"Let's see what is going to happen in the next round."

He relished having Cahill among his coaching staff as he eyed a deep run at Melbourne Park.

"It's very nice to have him here," Sinner said.

"Obviously he's a very important part of my team but the most important thing is he fits together with the rest of the team and I'm very happy to have them.

"Without them it's impossible to play at such a high level.

"We work every day harder - so let's go."

With AAP.