Melbourne, Australia (SportsNetwork.com) - World No. 1 Serena Williams didn't have it easy on Monday, but nonetheless advanced to the quarterfinals of the Australian Open.

Williams dropped the first set but rallied to top the 24th-seeded challenger and native of Spain Garbine Muguruza, 2-6, 6-3, 6-2 in a brisk two hours even. The 33-year-old American blitzed her 21-year-old opponent with 17 aces and won 38 of 49 first-serve points.

Her quarterfinal opponent will be 11th-seeded Slovakian Dominika Cibulkova, who dispatched Belarusian foe Victoria Azarenka by a 6-2, 3-6, 6-3 count in the earlier match at Rod Laver Arena.

Later action will see 18th-seeded Venus Williams squaring off against Agnieszka Radwanska and Madison Keys facing fellow American Madison Brengle.