Melbourne, Australia: Unseeded and floating dangerously in the draw, two-time Australian Open champion Victoria Azarenka took out No. 8-seeded Caroline Wozniacki 6-4, 6-2 on Thursday night to reach the third round at the first major of 2015.
Azarenka's ranking slipped into the 40s due to a series of injuries that restricted her to nine tournaments in 2014, meaning she didn't have a seeding at the Australian Open despite winning the title here in 2012 and 2013.
Former No. 1-ranked Wozniacki, who had never previously failed to make the third round in seven trips to Melbourne Park, reached the U.S. Open final last year before losing to Serena Williams.
"I knew that I'm unseeded so I can play anybody — I just accept whoever is on the opposite side," Azarenka said. "She had such an incredible end of last season so I knew I had to step up my game and really take my chances today. I think I did that pretty well."
Top-ranked Williams fended off three set points before going on a 10-game roll to beat Vera Zvonareva 7-5, 6-0 in another tough second-round match.
Men's No. 1 Novak Djokovic had an easier run, spending a minute less than Williams on Rod Laver Arena in his 84-minute, 6-0, 6-1, 6-4 win over No. 88-ranked Andrey Kuznetsov.
Defending champion Stan Wawrinka, who ended four-time champion Djokovic's 25-match winning streak at Melbourne Park in the quarterfinals last year, advanced to the third round for the seventh consecutive year with a 7-6 (4), 7-6 (4), 6-3 win over No. 194-ranked qualifier Marius Copil.
Wimbledon semifinalist Milos Raonic had a 6-4, 7-6 (3), 6-3 win over Donald Young to move into a meeting with Benjamin Becker, who came back from two sets down to end former No. 1-ranked Lleyton Hewitt's 19th consecutive run at his home Grand Slam tournament.
Fourth-seeded Wawrinka said he wasn't changing his approach despite the fact he's defending a major title for the first time.
"I don't compare from last year to this year. Just a new Grand Slam. It's been two matches now. Going to be ready now for the next one," he said. "That's it."
Williams, seeking a sixth Australian and 19th Grand Slam title, saved three set points in the ninth game before holding to swing the momentum of her match against Zvonareva, a two-time Grand Slam finalist who played only five tournaments in 2014.
That's when she told herself: "'You know Serena, you've done so well here, you have nothing to lose.'"
"Things really clicked. I had no other option but for things to click," she added. "Yeah, I just had to start playing better."
After breaking Williams' serve twice in the first set, Zvonareva only won eight points in the second set and didn't get close to another break-point chance.
Williams will next play No. 26 Elina Svitolina, who beat Nicole Gibbs 7-6 (3), 7-6 (6).
Venus Williams had a 6-2, 6-3 win against fellow American Lauren Davis. The elder of the Williams sisters, a seven-time major winner, hasn't been beyond the third round at a major since reaching the fourth round at Wimbledon on 2011.
Wimbledon champion Petra Kvitova, seeded No. 4, beat Mona Barthel 6-2, 6-4 to move into a third-round match against Madison Keys, who rallied to beat No. 29 Casey Dellacqua 2-6, 6-1, 6-1.
Sixth-seeded Agnieszka Radwanska needed only 44 minutes to race through her 6-0, 6-1 win over Johanna Larsson, continuing her run of reaching the third round or better at every Australian Open since 2010. In the next round, she'll face No. 30 Varvara Lepchenko, a 6-1, 7-6 (1) winner over Ajla Tomljanovic.
No. 11 Dominika Cibulkova, the 2014 finalist, No. 19 Alize Cornet and No. 24 Garbine Muguruza also advanced.
On the men's side, U.S. Open finalist Kei Nishikori beat Ivan Dodig 4-6, 7-5, 6-2, 7-6 (0) and will next face Steve Johnson, who defeated No. 30 Santiago Giraldo in straight sets.
No. 9 David Ferrer beat Sergiy Stakhovsky 5-7, 6-3, 6-4, 6-2, while No 12 Feliciano Lopez, No. 18 Gilles Simon, No. 19 John Isner and No. 31 Fernando Verdasco all advanced.
Jerzy Janowicz rallied for a 6-4, 1-6, 6-7 (3), 6-3, 6-3 win over No. 17 Gael Monfils.
