The first match of the day on Rod Laver Arena saw Victoria Azarenka beat Eleni Daniilidou.
Azarenka's controlled aggression produced 21 winners to 13 errors and a 61 60 scoreline.
Azarenka had lost her only previous meeting with Daniilidou, though it was five years ago.
Serena Williams followed on Rod Laver Arena with a 62 60 victory over Garbine Muguruza.
Angelique Kerber took some time out during her day off to meet fans and sign autographs.
Varvara Lepchenko, the No.20-ranked player in the world, also signed autographs this week.
Peng Shuai was on serve with Maria Kirilenko until the late stages of the first set.
But Kirilenko went on a seven game streak, going from 4-5 in that first set to 75 40.
No.14 seed Kirilenko made the third round, where she takes on No.20 seed Yanina Wickmayer.
Caroline Wozniacki stormed out to a 61 41 lead over Donna Vekic and closed it out, 61 64.
Svetlana Kuznetsova was also a winner, rolling over No.26 seed Hsieh Su-Wei, 62 61.
No.17 seed Lucie Safarova wasn't so lucky, getting upset by Bojana Jovanovski, 75 75.
Sydney champions Nadia Petrova and Katarina Srebotnik got off to a winning start in doubles.
Auckland champions Cara Black and Anastasia Rodionova also won their doubles opener.
And last but not least, 13-time Grand Slam champions the Williams sisters started with a win.