Updated

Defending champion Victoria Azarenka and 15-time major titlist Serena Williams were both easy second-round winners on Thursday at the Australian Open, but former Wimbledon champ Petra Kvitova was eliminated in a three-set thriller by rising British star Laura Robson.

The top-seeded Azarenka converted 5-of-8 break chances and took advantage of five double faults by Greek Eleni Daniilidou in a 6-1, 6-0 rout, while the third-seeded Williams continued her quest for a sixth Aussie crown with a 6-2, 6-0 pasting of Garbine Muguruza.

Williams, the reigning U.S. Open and Wimbledon winner, showed no ill effects after rolling an ankle in her opening match and powered past the Spaniard on Thursday with 10 aces and just one double fault. She'll next meet Japan's Ayumi Morita, who thumped Germany's Annika Beck, 6-2, 6-0.

"It feels better," Williams said about the ankle. "I was just doing everything you can do (to get ready for today)."

Azarenka, meanwhile, finished her match Thursday in a mere 55 minutes and will next square off against American Jamie Hampton, a 6-1, 6-2 winner over Thailand's Luksika Kumkhum.

"I was in the zone trying to execute all of my shots," said Azarenka about her play Thursday. "I was trying to make everything happen, and that's what I'm happy about."

Kvitova, the 2011 Wimbledon winner and a semifinalist in Melbourne last year, cruised through the first set against Robson in just 38 minutes, but couldn't finish off the 18-year-old Melbourne native. Robson went deep into the night at Rod Laver Arena to complete a 2-6, 6-3, 11-9 victory that ended well after midnight, local time.

Robson appeared out of it in the third set, down 1-4, but she rallied and grabbed a 6-5 lead to serve for the set. Kvitova, though, broke serve to keep the match going, and on it went. Eight more games as a matter of fact.

Finally, Robson broke serve for a 10-9 lead and held at love to close it out in exactly three hours.

Next up for Robson will be American teenager Sloane Stephens. The 19-year-old Florida native advanced with a 6-4, 6-3 win over Kristina Mladenovic. Stephens and Robson met just last week at the tune-up in Hobart and the American came away with a 6-4, 7-6 (7-4) triumph.

Former world No. 1 Caroline Wozniacki was another straight-set winner Thursday with a 6-1, 6-4 decision over Croatia's Donna Vekic. The 10th-seeded Dane capitalized on 32 unforced errors by her opponent to advance and will face Lesia Tsurenko of the Ukraine, a 7-5, 6-3 winner over Russian Daria Gavrilova.

Maria Kirilenko and Roberta Vinci were other seeded winners Thursday.

The 14th-seeded Kirilenko dumped China's Shuai Peng, 7-5, 6-2, and will next play Belgium's Yanina Wickmayer, a 7-6 (10-8), 7-5 winner over Slovakia's Jana Cepelova. Vinci, the 16th seed, notched a 6-3, 6-2 triumph over Uzbekistan's Akgul Amanmuradova to earn a date with Russia's Elena Vesnina, who is coming off her first WTA title last week in Hobart and on Thursday advanced with a 6-4, 6-2 win over American Varvara Lepchenko.

Russian veteran Svetlana Kuznetsova earned her second straight easy win this week, roaring past Taiwan's Su-Wei Hsieh, 6-2, 6-1. Unseeded this fortnight, Kuznetsova has dropped just six games in her first two matches and will next face Spaniard Carla Suarez Navarro, who followed up her first-round upset of seventh-seeded Sara Errani with a 1-6, 7-6 (7-5), 6-2 win over Kazakhstan's Yulia Putintseva.

Also, Japanese veteran Kimiko Date-Krumm captured a 6-2, 7-5 win over Israel's Shahar Peer and will next play Serbia's Bojana Jovanovski, a 7-5, 7-5 winner over 17th-seeded Czech Lucie Safarova.

The third round starts Friday with a blockbuster between Maria Sharapova and Venus Williams highlighting the schedule. The second-seeded Sharapova has yet to drop a game in her first two matches, while the 25th-seeded Williams has lost only seven games in her first two.

Also Friday, fourth-seeded Agnieszka Radwanska takes on Heather Watson, fifth- seeded Angelique Kerber meets American Madison Keys, sixth-seeded Li Na faces Sorana Cirstea and Ana Ivanovic battles fellow Serbian Jelena Jankovic in a matchup of former world No. 1s.