Melbourne, Jan 22: Former World No.1 Roger Federer dug in his heels to stop Japanese Kei Nishikori, rallying past the fifth seed 6-7(4), 6-4, 6-1, 4-6, 6-3, to enter the quarter-finals of the Australian Open tennis tournament here on Sunday, January 22.

Federer, the 17-time Grand Sam winner, won in three hours and 23 minutes.

Federer secured a milestone 200th win over a top 10-ranked opponent, becoming the first active player to achieve the feat.

"He played his heart out and I thought he played a great match, I'm happy to be a part of it," Federer was quoting as saying by atpworldtour.com after his match.

"He was hanging tough and playing really well on the big points. I was telling myself to stay calm and this is what I trained for in the off-season. This is a big moment for me in my career."

The four-time champion exhibited great resolve in fighting back.

He will feature in the quarter-finals at Melbourne Park for the 13th time in the last 14 years, with a date against German Mischa Zverev, who stunned World No.1 Andy Murray earlier on Sunday, awaiting on Tuesday.

Federer have won their previous two encounters against Zverev.

IANS