Welcome to the big time, Stefanos Tsitsipas.

The 20-year-old Greek has been making waves for his nation ever since he burst onto the tour but on Sunday in Melbourne, his stunning 6-7(11), 7-6(3), 7-5, 7-6(5) win over Roger Federer prompted John McEnroe to hail it as the “changing of the guard”.

The man who has won 20 Grand Slam singles titles, more than any man in history in what has been a golden era for men’s tennis, found himself on the losing end against Tsitsipas, who played the match of his life on the biggest stage of his life.

“I’m the happiest man on earth right now,” Tsitsipas said. “I have been idolising Roger since the age of six. It was a dream just being on Rod Laver, and facing him, and winning at the end, it’s indescribable.”

Crunching serves and keeping Federer off balance with huge backhands and powerful forehands, he mixed up his game well, too, raiding the net on 68 occasions, winning 48 of them. Even as Federer stepped up the pressure, he never stopped believing and when he had the opportunity, he grabbed it hungrily.

As a keen student of tennis history, Federer will recognise the similarities between his loss to Tsitsipas and his own win over Pete Sampras at Wimbledon in 2001, a match which was the beginning of the end for the American, and the first signs of what he would go on to achieve himself.

Like 2001, this was a fourth-round match. Both Federer, in 2001, and Tsitsipas here in Melbourne, were ranked 15; both had won one title in their career coming in and until they started their respective events, neither had won a match there before.

 This was the performance of a future champion, a man destined for the top.

Patrick Mouratoglou, who works with Tsitsipas at his academy in France, believes the Greek can go all the way to the top, having first seen him play via YouTube, before quickly inviting him to his academy.

His determination and willingness to work hard and compete, fighting for everything, was what first impressed Mouratoglou, and even against Federer, he never stopped moving forward, taking the attack to the Swiss, whose biggest problem was not taking one of his 12 break points.

Nevertheless, Federer, who had won the title in each of the past two years, looked in control after he won the first set on the tiebreak, 13-11, saving three set points in the process.

But Tsitsipas stayed strong, holding several tight service games and fighting off more break points to stay in touch in the second and when the tiebreak came round, he snatched it 7-3.

“I felt like I had to win the second set,” said Federer, who expressed “massive regrets”. “I thought, I don't care how I do it, but I have to do it. That cost me the game tonight.”

One break gave Tsitsipas the third set and in the fourth set, as Federer tried everything he could think of, he stayed strong, never stopped believing and got himself over the line for the biggest win of his young career.

Federer said the cooler evening conditions may have played a part. “I lost to a better player who was playing very well tonight,” he said. “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.

“Conditions also changed throughout the match like every year when you start at 7, go into the night. It gets harder to go through the opponent. I thought conditions were definitely a bit slower this year than last year. Didn't allow for as much variation, to be quite honest.”

With Novak Djokovic and Rafael Nadal still going strong as the top two in the rankings – and here at the Australian Open – it might be too soon to be a true changing of the guard.

But Tsitsipas is the real deal and even Federer accepted the comparison.

“I guess so. He has a one-handed backhand and I used to have long hair too,” Federer said. “Maybe a little bit, he does have more of a continental grip than players nowadays, which is a bit more my way than say, Rafa (Nadal)’s way.”

At 37, Federer knows better than anyone how much he has left in the tank, how much longer he wants to go through all the travel, the rigours of the tour.

His ranking will fall to No.6 but he said on Sunday that he now plans to play on clay this year, including a first appearance at the French Open since 2015. “I’m in a phase where I want to have fun, and I don’t feel like I need to make a big break.”