He had to contend with the heat, which hit 30 degrees, as much as Tsitsipas and his superb fitness held him in good stead. Ever since his young years, tennis became his life.
"I feel lucky to be where I am after all the things I went through", said Nadal, who quit during his quarterfinal at Melbourne Park a year ago because of a right leg problem, again during his semifinal at the U.S. Open in September because of a painful right knee, and then had off-season surgery on his right ankle. "I'm living a dream, living what I worked so hard for. Winning at the end, I can't describe it".
The result may come to symbolise the changing of the guard with Tsitsipas eclipsing his previous best Grand Slam record of reaching the fourth round at Wimbledon past year.
At least Federer was able to crack a joke when asked whether Tsitsipas reminds him of a younger version of himself, replying: "He has a one-handed backhand".
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I just told myself I'm going to die or win so it was just a mental game. "And I'm normal too", she said. Japan's Naomi Osaka reacts during her match against Latvia's Anastasija Sevastova .
He won a long rally with a forehand onto the line to save a match point at 5-6 in the fourth set, Tsitsipas paying the price for playing a little too conservatively. "He's a very dynamic player, aggressive one".
And as is often the case when a youngster outdoes an old master, there was a buzz about whether this might signal something more meaningful.
Stefanos Tsitsipas has been slow out of the blocks in his quarterfinal against Roberto Bautista Agut, dropping serve in the opening game of the match and being forced to really fight not to go behind a double break.
"Tsitsipas is doing very well", said Bautista Agut.
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.
Nadal had never faced the World No 39 before, but decided rather than feel his way into the match, he would bludgeon Tiafoe from his path.
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However, Tsitsipas quickly rose to the occasion, breaking back to level at 4-4 before sealing the first set with another break in the 12th game. He will next play American Frances Tiafoe.
Rafa Nadal kept the flag flying for the old guard at the Australian Open with a 6-3, 6-4, 6-2 win over American Frances Tiafoe on Tuesday.
It's insane. I didn't think any of this was going to happen.
Spaniard Nadal, who avenged his defeat to the former world number four in the quarter-final of the 2015 tournament, sealed the win on his first match point when the Czech hammered into the net.
Tiafoe, who is from Maryland, was broken the initial time he served in each set, which was all Nadal needed, given how well he handled his own service games.
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