Stefanos Tsitsipas had to apologise for an expletive-laden rant at the Australian Open as he set up a fourth-round clash with Roger Federer.

Twenty-year-old Tsitsipas is arguably the most exciting young talent in men's tennis and his meeting with defending champion Federer on Sunday will be one to savour.

But the young Greek also has a temper and, after the umpire decided to replay a set point for Tsitsipas during his clash with Nikoloz Basilashvili at 5-3 in the third set, the 14th seed let rip.

Melbourne's Greek population have turned out in numbers to support Tsitsipas and his countrywoman Maria Sakkari, and there were a lot of young fans in Margaret Court Arena.

Pressed on his language afterwards, Tsitsipas said: "It was heat of the moment. I said some really bad things. I regret saying them. But I really wanted this really bad.

"At that moment it felt like it was slipping (away). He kind of found comfort and confidence after that. So I was really frustrated. I didn't quite think what I was saying. I wish I could change that and wouldn't say that. It's not the right attitude."

Among a talented generation, Tsitsipas stands out with his flowing curly locks and flamboyant game, but it is his fighting spirit that is perhaps his greatest asset and he showed it in abundance to beat the dangerous Basilashvili 6-3 3-6 7-6 (7) 6-4.

Federer and Tsitsipas have never played a competitive match but they each know what to expect from the other having contested a high-level encounter at the Hopman Cup earlier this month.

Tsitsipas knows he must be prepared not just physically but mentally, saying: "If I thought about it now it's insane I'm in this position where I can actually play him. It's really emotional.

"It's not easy to play these kind of players that you've been watching for so long. Mentally you have to be much stronger than any other match. For players to beat him, they have to be ready and believe in themselves that they are, their game is great enough to beat such a player."

So does he believe?

"I feel good, I can tell you that," he added.

Tsitsipas was not born when Federer began his professional career but the 37-year-old continues to make top-level tennis look ridiculously easy and his 6-2 7-5 6-2 victory over young American Taylor Fritz, during which his four-year-old son Lenny made a rare appearance, was full of highlight-reel shots.

The third seed is excited to be taking on Tsitsipas, saying: "I'm happy I played against him at the Hopman Cup. I think he played really well there. I actually did, too. I thought it was really high-quality tennis. This is obviously a different type of match.

"I'm happy for him. He's playing so well, and I'm looking forward to the match-up with him. I like how he mixes up his game and also comes to the net. I think we will see some athletic, attacking tennis being played."

A resurgent Tomas Berdych is also through to the last 16 after a 5-7 6-3 7-5 6-4 victory over 18th seed Diego Schwartzman.

Berdych missed the second half of last season with a back injury but has a strong record in Melbourne having reached at least the quarter-finals in seven of the last eight seasons.

Grigor Dimitrov continued to take advantage of his favourable draw, beating Italian Thomas Fabbiano 7-6 (5) 6-4 6-4 to set up a last-16 meeting with America's Frances Tiafoe.

The 20-year-old was in tears on court after backing up his big victory over Kevin Anderson by coming from two sets to one down to defeat Andreas Seppi.