Motivated by a Grand Slam loss that stung her more than most, Serena Williams dug deep for a 2-6, 6-3, 6-2 comeback win over Garbine Muguruza on Monday to reach the Australian Open quarterfinals.

The top-ranked Williams was pushed all the way by No. 24-seeded Muguruza, who matched her in the heavy-hitting stakes, and who had conceded only four games to her in a second-round upset last year at the French Open.

Five-time Australian Open winner Williams next faces Dominika Cibulkova, who reproduced the kind of tennis that took her to the final here last year as she beat two-time champion Victoria Azarenka 6-2, 3-6, 6-3.

Defending champion Stan Wawrinka beat Guillermo Garcia-Lopez 7-6 (2), 6-4, 4-6, 7-6 (8) to move into the men's quarterfinals, where he'll play U.S. Open finalist Kei Nishikori

Spurred on by hundreds of flag-waving Japanese supporters at Rod Laver Arena, No. 5-ranked Nishikori had little trouble in a 6-3, 6-3, 6-3 win over No. 9 David Ferrer, who reached the French Open final and Australian Open semis in 2013.

His routine win was unlike the three-setter Williams endured, when she appeared to be laboring and had a serious cough. Williams struggled with her serve in the first set, winning only one of a dozen points on her second serve. She couldn't convert her six break-point chances, while Muguruza broke her twice.

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