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Lest anyone get the idea that Tsitsipas' stunning victory over Federer at Melbourne Park was a fluke, he followed it up by becoming the first player from Greece to reach the final four at a major tournament.

"I knew that win against Federer was important, played a huge role in my image -- like, who I am," said Tsitsipas, who eliminated the Swiss in the fourth round Sunday. "But I knew that the biggest challenge was today's match, that I can prove myself once again."

Cheered on by a loud, flag-waving contingent of Greek fans inside and outside Rod Laver Arena, Tsitsipas displayed his varied toolbox, producing 22 aces, 30 more winners than unforced errors (68-38) and a nose for getting to the net.

It was a terrific encoreto what he did against his idol, the 37-year-old Federer, in a result that left Tsitsipas unable to sleep.

Tsitsipas was down a break in the first and third sets before turning both around against Bautista Agut, whose own thrill ride to the quarterfinals included victories over three-time major champion Andy Murray and Marin Cilic, the 2014 US Open champion and the runner-up to Federer at Melbourne Park a year ago.

"Well, he's a good player, no? He's very complete. He has a good forehand and backhand. He's serving well," Bautista Agut said about Tsitsipas. "I think he knows the game. He knows how to play."

That's why his peers voted him the 2018 Most Improved Player. And why he's already in the top 20, seeded 14th in Australia.

Stefanos Tsitsipas, 20,