Sofia Kenin, Belinda Bencic and Elise Mertens were all beaten at the Volvo Car Open, where Ash Barty moved through.
Second seed Naomi Osaka benefited from a walkover after Nina Stojanovic withdrew ahead of Sunday's clash due to a right thigh injury.
After losing in the second round at Melbourne Park last week, American star Sofia Kenin had an operation.
On another warm day in Melbourne, there were contrasting results for star duo Sofia Kenin and Ash Barty in the second round.
After her Australian Open title defence came to an end, Sofia Kenin said the pressure was too much for her.
Kaia Kanepi ended Sofia Kenin's title defence at the Australian Open.
Garbine Muguruza and Sofia Kenin reached the second round, while Victoria Azarenka bowed out of the Australian Open.
Serena Williams is still waiting for a 24th major singles title but Ana Ivanovic is confident the American will reach that tally.
Sofia Kenin menegaskan bahawa kecederaan kakinya semalin pulih ketika dia bersedia untuk mempertahankan kejuaraaannya dalam Kejohanan Tenis Terbuka Australia.
As she prepares to defend her title at the Australian Open, Sofia Kenin discussed her injury worry.