The 34-year-old Belarusian came back from second set jitters to see off Russia's Anna Kalinskaya 6-1, 7-6 (10/8).

Azarenka had been in complete control early, racing to a 5-0 lead before wrapping up the first set.

A two-time winner of the Australian Open, she then got an early break in the second set and appeared to be cruising.

But Kalinskaya began to find her range as Azarenka faltered, failing to hold while serving for the match at 5-4 and 6-5.

The tiebreak was just as dramatic, with Azarenka having five match points before getting over the line.

Kenin, also a former Australian Open winner, was stunned by Rodionova, who had a successful year on the lower-level ITF Circuit, winning seven titles and taking her ranking to a career-high 113.

She has brought the form into the season-opening tournament, beating opening round opponent Martina Trevisan before outlasting a rusty Kenin, who made 52 unforced errors in the 7-5, 7-6 (9/7) defeat.

Rodionova said playing in front of a big crowd on Pat Rafter Arena was reward for the hard work put in on the ITF Circuit.

"I think that's the reason why I'm having so much fun out there because, as I say, I've done the hard work," Rodionova said.

"I've played in the small cities, small tournaments where no one is watching."

There were also upsets in the men's draw with fifth-seeded American Sebastian Korda and Argentinian sixth seed Sebastian Baez both crashing out.

Germany's Yannick Hanfman downed Korda 7-5, 6-4 while Baez lost to Lukas Klein, with the Slovakian qualifier winning 4-6, 6-3, 6-4.

Australian qualifier James Duckworth also enjoyed a good win by ousting American JJ Wolf 6-3, 6-4.