Serena Williams overcame a sluggish start to beat Anastasia Potapova and reach the Australian Open fourth round.
Tenth seed Williams, bidding for a record-equalling 24th Grand Slam title.
However, the American had trailed 5-3 in an error-strewn first set, and she had to save two set points before dialling back in to win.
Naomi Osaka also advanced after a cagey match against Ons Jabeur of Tunisia.
Third seed Osaka and her opponent struggled for rhythm but it was the Japanese who prevailed in the end.
Osaka will face two-time Grand Slam champion Garbine Muguruza next, while Williams plays seventh seed Aryna Sabalenka for a place in the quarter-finals.
She will face a tough test against big-hitting Belarusian Sabalenka, who beat American Ann Li.