From the land of Homer has come a charming young man with a taste for the epic and the theatrical. Stefanos Tsitsipas has style and not merely because he resembles a long-limbed, long-haired hippie who thinks net play is cool. But because he knows how to make defiant and dazzling introductions.

On a cool Sunday night at the Australian Open, the 20-year-old Greek told the wider world who he was by beating the best player ever, in an arena he owns, in front of legends who love him, before a crowd ready to adopt him. Beating Roger Federer in Melbourne always takes nerve. As the Greek said: "My idol today became pretty much my rival."

Has the guard changed in tennis, people are wondering, but this was not a night about a legend departing but about a young talent arriving. Tsitsipas idolised Federer and then showed him how much he had learnt by beating the Swiss 6-7 (11-13), 7-6 (7-3), 7-5, 7-6 (7-5) in the fourth round. He was the younger man, the faster man and simply the better man.

At the end, a smiling, dazed Tsitsipas stood on the court, his joy laced with relief, holding back his tears as he had held back the Swiss. "I am the happiest man on earth," he said and covered his mouth in disbelief. When dreams come true, words dry up. He had always believed he could win but still he was incredulous that he had.

Later, he was asked if he could go all the way and he replied: "For sure. That's why I'm here. That's why I'm playing, for the trophy."

Federer arrived first in the press room, his face a quiet painting of loss. Nothing ages like defeat. It will take him a while to forget that he had 12 break points on Tsitsipas' serve but couldn't convert even one. It was like he could remember how to create but not how to finish. Genius doesn't fall apart, it gently fades.

At 37, every lost chance cuts deeper but even in such a moment the Swiss wrapped himself in decency. "I lost," he said, "to a better player who was playing very well tonight. Hung in there, gave himself chances at some point, stayed calm. It's not always easy, especially for younger guys. Credit to him for taking care of that."

One man, the world No. 15, was fighting to be the future and the other, world No. 3, not to be the past. Expectedly desperation littered the court. The first game itself took eight minutes and 14 points, involved two time violations for Tsitsipas for taking too long to serve and one "I love you, Roger" from an overcome lady.

Both these men were wedded to aggression and allied in their willingness to visit the net. As Federer dryly remarked when asked about any similarities with Tsitsipas: "He has a one-handed backhand and I used to have long hair, too. Yeah, so maybe a little bit, sure."

But mostly it is age and experience which divide these men. The Greek is playing only his seventh Slam and Federer has won 20. Indeed, it is possible that Federer, 37, has CDs in his attic older than Tsitsipas but eventually he couldn't make the Greek dance to his tune.

The tennis was always electric and unrelenting, like toe-to-toe boxing in a large ring. Both men coloured the court with greatness as they hit 123 winners together and played 134 net points, but like always the match was decided by the big points.

Federer somehow won the first set with a lovely, low punched volley, shanked forehands and a drop shot, but then couldn't break Tsitsipas. Over three successive games in the second set the Swiss had eight break points - four of them set points - but the Greek wouldn't flinch. His aggression was irresistible and his speed of shot and foot was sensational. He gave Federer his respect but never his awe.

"It was actually very mental," said Tsitsipas later. "I could have cracked at any moment, but I didn't because I really wanted it bad."

Federer needed that second set and the momentum that would have come with it and later he admitted it: "I have massive regrets, you know, tonight. I might not look the part, but I am. I felt like I have to win the second set. I don't care how I do it, but I have to do it. Cost me the game tonight."

Tsitsipas won the second-set tie-breaker, broke Federer in the last game of the third set to win it 7-5 and edged him in the fourth set tie-breaker. The crowd pleaded with the Swiss but Federer had run out of shots and comebacks. He was that rarest of things in a long career: not good enough.

Tsitsipas has introduced himself and now he has to establish himself. Later, he said: "For sure it's a good win against Roger. I mean, we all know who Roger Federer is, what he has done in tennis. But I still have to keep my focus, keep my concentration on further goals that I want to achieve. That's a very good beginning. I need to stay humble."

At 1.25am, Tsitsipas was still doing interviews in the press room. Outside applause broke the silent night as a women's match continued. So much had changed in a few hours and yet the tennis always goes on. Federer's journey in the game had not ended, only a Greek odyssey had triumphantly begun.