Serena Williams breezed into the Australian Open third round but Petra Kvitova and Bianca Andreescu were the biggest casualties on the third day.
American Williams, who has dropped just five games in her two matches so far, beat Serbia's Nina Stojanovic 6-3 6-0.
Czech ninth seed Kvitova, who reached the final in 2019, was stunned 6-4 1-6 6-1 by Sorana Cirstea of Romania.
Andreescu, playing in her first major since winning the 2019 US Open, lost 6-3 6-3 to tricky Taiwanese Hsieh Su-wei.
Last year's finalist Garbine Muguruza continued her good form on the hottest day of the tournament so far with a 6-3 6-1 win over Russian Liudmila Samsonova.
Belarusian seventh seed Aryna Sabalenka also advanced, beating Daria Kasatkina of Russia 7-6 (7-5) 6-3.
