Melbourne, Jan 21 (AFP) Relentless Rafael Nadal will aim to snuff out the challenge of young giant-killer Frances Tiafoe Tuesday, while young Greek Stefanos Tsitsipas has eyes on a maiden Australian open semi-final after knocking out Roger Federer.

The Australian Open hits the quarter-final stage in Melbourne with 17-time Grand Slam winner Nadal emerging as a strong title favourite.

The Spaniard has not dropped a set and demolished former world number four Tomas Berdych 6-0, 6-1, 7-6 (7/4) in the fourth round in an awesome display.

Lying in his path is American Tiafoe who has already accounted for the fifth seed Kevin Anderson and become a fans' favourite with his exuberant LeBron James style celebrations and inspiring life story.

The son of immigrants from Sierra Leone, Tiafoe turned 21 on Sunday and celebrated his birthday by beating 20th seed Grigor Dimitrov to reach a Slam quarter-final for the first time.

"I wasn't a normal tennis story," he told reporters, revealing he had already managed to buy his mother a house in Maryland and help his janitor dad.

"The beginning of my career I was trying to do everything for my family. Obviously now I put them in a great place. Now I'm trying to do it for me.

"I'm so excited to play Rafa. We're going to have some fun, going to have some long rallies."

Nadal said he was aware of the young world number 39, and would be on his guard against a man he had never played.

"He has everything. He's quick. He serve well. Very quick forehand," said the 2009 champion who is aiming to become the only man in the Open era to win all four Grand Slams at least twice.

- 'He's dangerous': Nadal -

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"He's a very dynamic player, aggressive one. Of course, he's dangerous. He's in quarter-finals."

Tsitsipas was thrust into the global spotlight after ending double defending champion Federer's quest for a record seventh Australian Open.

The gifted 20-year-old has already secured his place in history as the first Greek to reach a Grand Slam quarter-final.

He held off 12 break points before flummoxing the Swiss master in four sets.

"This win is a good milestone, let's say good first step to something bigger," said the exciting 2018 NextGen Champion.

"I'm really pumped and excited to be competing in the quarter-finals. I'm really waiting for that moment."

He faces another Spaniard, the in-form Roberto Bautista Agut.

The 22nd seed beat Novak Djokovic on his way to the title in Doha earlier this month before ending Andy Murray's hopes, and possibly his career, in the first round in Melbourne.

Bautista Agut is looking to extend his 2019 win streak to 10 matches and a potential all-Spanish semi-final against Nadal.

"Tsitsipas is doing very well," said Bautista Agut. "He's one of the top players in the world. He will be one of the best, for sure. He's playing at a very high level." (AFP) ATK

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