Melbourne, Jan 20 (IANS) Unseeded Frances Tiafoe celebrated his 21st birthday by booking his maiden Grand Slam quarterfinal at the Australian Open here on Sunday after routing Bulgaria's Grigor Dimitrov.

He overpowered the former world number three 7-5, 7-6(6), 6-7(1), 7-5 in three hours and 40 minutes, to become the first American since Andy Roddick nine years ago to reach the last eight in Melbourne, reports Efe news.

"It means the world. I worked my ass off, man," he said after the match.

"I told my parents 10 years ago I was going to be a pro and change my life, change their life. Now I'm in the quarters of a slam at 20 years old - 21 years old - I can't believe it, man," he added.

He will now play against number two seed Rafael Nadal, who beat former world number four Tomas Berdych on Sunday.

--IANS kk/bg