A version of this article was initially published on 19 January

In pursuit of his dream to become Greece’s first Grand Slam singles champion, Stefanos Tsitsipas was glued to his computer screen.

Watching YouTube footage of his idol Roger Federer was one method he chose as he sought to become one of the world’s best players.

His favoured match? The then-teenager Federer’s victory over the great Pete Sampras at Wimbledon in 2001.

So it is quite apt that Tsitsipas’ fourth-round triumph at the Australian Open is – like Federer’s landmark win – being hailed as a ‘changing of the guard’ moment.

A similar age, a similar ranking and, as Federer mentioned afterwards, similar hair.

From studying him on YouTube to beating him at a Grand Slam, here’s how Stefanos Tsitsipas has become one of the most talked about talents in tennis…

‘You can see the impact of Federer’

No Greek man had ever reached the world’s top 100 until the then teenager cracked it in October 2017, never mind anywhere near his current ranking of 15.

Tsitsipas’s rise up the rankings transferred into trophies when he won his first ATP Tour title at the Stockholm Open last October, bettering that – and garnering more attention across the world – with victory in the NextGen Finals in December.

His 6-7 (11-13) 7-6 (7-3) 7-5 7-6 (7-5) victory over Federer is the biggest sign of what he is capable of, and he could climb into the world’s top 10 if he makes it past Spain’s Roberto Bautista Agut in his quarter-final.

Greek journalist Vicky Georgatou, who first met him as a teenager, said he was always destined for the top.

“When I first saw him play, I knew he would do something big,” Georgatou told BBC Sport.

“Most of the kids play with two-handed backhands. When I saw him playing with the one-hand backhand I loved it.

“He plays old-school tennis, he has a very good forehand, that is his strength, but he also serves well and has that beautiful backhand which is powerful too.

“He has variety in his game, he goes to the net, he volleys a lot, he can be unpredictable.

“Sometimes his style reminds me of Federer. He was his idol and he watched him a lot. You can see the impact of Federer.”

‘I’d love to have more friends on tour’

A playing style described as “old-school”, his own travel vlog, a love of photography, a flowing mane of hair… Tsitsipas has been one of the most talked about young talents on the ATP Tour – even before Sunday’s victory over Federer.

After his third-round win over Georgia’s Nikoloz Basilashvili, Tsitsipas admitted he did not have many friends in the locker room.

“I think I’m comfortable meeting new people and having a discussion with someone,” he said when asked about his perceived shyness.

“Not many of the players want to be friends on the tour. That’s a problem.

“That’s an issue unless you speak the same language. That makes sense.

“But I would love to have more friends on tour.”

Georgatou, who works for Greek sports website SDNA, says that being what some might term a “loner” is nothing new for Tsitsipas.

“His father told me when Stefanos was a little boy he didn’t have many friends,” she told BBC Sport.

“But he liked it that way. It wasn’t a problem.

“He’s not like the other guys on their phones, playing games, he likes to take pictures, he likes to read, he’s very different.”

Carrying the hopes of a nation – and inspiring it

Greece had never made a major dent on the men’s tennis circuit until Tsitsipas announced his arrival last year.

But it seemed clear that he would end up becoming a beacon for tennis in his nation from a young age.

Born into a tennis family, his mother Julia Salnikova was a Fed Cup player for Russia, his father Apostolos was – and still is – his coach, Tsitsipas first picked up a racquet aged three.

Georgatou, who works for Greek sports website SDNA, says even when she first met him as a teenager he had plans to inspire a tennis revolution back home.

“When he was young said he wanted to become a top-10 player and make kids play tennis in Greece,” she said.

“Greece is a country where people are crazy about football and basketball – that will never change.

“I believe that now Stefanos is doing well – and Maria Sakkari too [the Greek women’s number one] – it will become the number three sport in Greece and people will start watching it.

“Hopefully that will lead to more kids picking up a racquet and playing.”

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‘Raucous support can distract him’

Winning trophies and being ranked among the world’s best players has already seen Tsitsipas attract fervent support here in Melbourne – a city known for its large Greek community.

During his opening three matches he was backed by an enthusiastic crowd regularly chanting football terrace-style and unfurling several blue-and-white Greek flags when they got the chance.

Against Federer, fans were largely congregated outside Rod Laver Arena, watching and cheering the action on the big screen.

“He always tells me that he is playing for the flag – he is a very proud Greek boy,” she said.

“I think he’s not crazy about all this attention, I’m not sure he felt pressure but he’s not used to it.

“He likes feeling loved by people but I think sometimes he gets distracted.

“He told me the first match was difficult and then I think he got used to it.

“He’s a quiet boy, he prefers the tennis the way it is.”