Veteran tennis champ John McEnroe wasn’t wrong on Sunday night when he declared a “changing of the guard!” in tennis, following Stefanos Tsitsipas’ win against Roger Federer.

The Greek 20-year-old is proving to be unstoppable, successfully charging through the Australian Open quarterfinals on Tuesday, beating his Spanish opponent Roberto Bautista Agut.

It was a hard-fought four sets, the young gun winning 7-5, 4-6, 6-4, 7-6 (7-2).

Until the day nine match up, Bautista Agut, who is ranked 24, had yet to lose a match this year, winning nine matches in a row. But his winning streak was brought to an end by the talented young Greek. This is the first time the players had met on the court.

Both players caused upsets in the fourth round of the Grand Slam, which saw Tsitsipas beat his tennis idol, 20-time Grand Slam champion Federer, while Bautista Agut managed to defeat Marin Cilic, last year’s Australian Open runner-up.

Having played three five set marches in the tournament, in the lead up it was suggested the 30-year-old Spaniard might be fatigued by the time he came to face Tsitsipas, but he continued to do his best to fight until the very end.

Yes, you @StefTsitsipas!

You're into the #AusOpen quarterfinals 👏 pic.twitter.com/n9FJwedn0O

— #AusOpen (@AustralianOpen) January 20, 2019

The Greek community of Melbourne has rallied around Tsitsipas throughout the tournament so far, dressed in blue and white, and proudly donning their Greek flags.

READ MORE: Who is Tsitsipas? And why are Greeks making so much noise about him?

Greek fans celebrate at Garden Square, Melbourne Park as their hero ⁦@StefTsitsipas⁩ takes a two sets to one lead in the ⁦@AustralianOpen⁩ quarters ⁦@TOISportsNews⁩ ⁦@VGeorgatoupic.twitter.com/t8nQr9gAQv

— Prajwal Hegde (@prajhegde) January 22, 2019