Melbourne, Jan 26 (IANS): World No.1 and top seed Serena Williams overcame a massive threat from rising star Garbine Muguruza to win 2-6, 6-3, 6-2 and enter the quarter-finals of the women's singles category at the Australian Open tennis tournament at the Melbourne Park here Monday.

Muguruza, the 24th seed, condemned Serena to her career's worst Grand Slam loss at last year's French Open, allowing her just four games in an absolute rout in the second round and the first round Monday evoked memories of that match, with Muguruza winning it 6-2 at the Rod Laver Arena.

But Serena fought her way back.

The No.1-seeded Williams stayed even with Muguruza through 3-all in the second set before breaking away to take it, 6-3. She dug her way out of an absolute marathon of a 0-1 service game in the third - she had to fight off six break points in that eight-deuce game - she started to roll, eventually finishing the No.24-seeded Spaniard off after exactly two hours on the clock, 2-6, 6-3, 6-2.

"It was a great match - congratulations to Garbine, she played so well," Williams said.

"She did everything she needed to do in the first set. For once I didn't start out slowly, she was just playing so well at the start. She hits the ball really, really big and really, really hard.

"But I started to focus from there and just relaxed a little bit."