Australian Open 2019: Birthday boy Tiafoe to face Nadal in first Grand Slam quarter

Melbourne: An emotional Frances Tiafoe celebrated his 21st birthday Sunday in style by beating 20th seed Grigor Dimitrov to reach the quarter-finals of a Grand Slam for the first time and a meeting with Rafael Nadal.

The American world number 39 broke down in tears after stunning the Bulgarian in the fourth round of the Australian Open 7-5, 7-6 (8/6), 6-7 (1/7), 7-5 in 3hr 39min.

"It means the world," said Tiafoe, voice cracking. "I worked my ass off, man."

Tiafoe is the son of immigrants from Sierra Leone and his father works as a janitor.

"I told my parents 10 years ago I was gonna be a pro tennis player and change their life," he said.

"Now I'm in the quarter-finals of a Slam. I can't believe it."

The aggressive American upset the 20th seed in four high-quality sets that saw multiple breaks of serves and an avalanche of breathtaking winners.

"I would have been mad if I had lost on my birthday," he added.

Tiafoe was on the front foot from the start and took the first set after 52 minutes and marked it with a one-arm raised fist salute.

Dimitrov hit back at the start of the second but double-faulted at 4-2, 30-40 to squander the early break to the consternation of coach Andre Agassi in his player box.

It got worse when the 27-year-old, once dubbed BabyFed because of his smooth backhand reminiscent of Roger Federer, blew three set points at 6-3 in the tiebreak.

Tiafoe took advantage and ripped a winner on his first set point to create a two-set cushion and then posed in admiration at his own work.

Power-packed Tiafoe squandered a break in the third and was in trouble again at 4-4, deuce until he unloaded a crosscourt forehand into the corner at deuce with such venom it almost tore the fur from the ball.

A sweet volley to go to 5-4 was met with a beaming smile to his box and the set headed for another tiebreak.

Dimitrov this time raced to 6-1 and got himself back in the match on his first set point as Agassi leapt to his feet and smacked the barrier in front of him in a mixture of relief and delight.

Another attritional set ensured until at 5-5 Tiafoe, who played in the recent mixed teams Hopman Cup with Serena Williams, secured the decisive break and served out to set up a last-eight clash with number two seed Nadal on Tuesday.

After celebrating by ripping his shirt off, beating his chest and showing off his muscles, LeBron James-style, Tiafoe seemed almost embarrassed.

"I said I wasn't going to do that again," he grimaced.

He admitted he will have no chance of celebrating his birthday as he will have to prepare for the daunting prospect of facing the 17-time Spanish Grand Slam champion.

"I can't do anything tonight. He's going to run me like crazy," he said.

"I'd better go to bed now."