Former world number Karolína Plíšková feels like she is slowly warming to the task after storming into the Australian Open’s second week for the first time in four years.

Runner-up to Ash Barty in the 2021 Wimbledon final, Plíšková pounded down six aces and bossed Varvara Gracheva from the back of the court in a 6-4, 6-2 dispatch of the Russian on Saturday.

The Czech landed 72 per cent of her first serves and won 82 per cent of those points in an ominous warning to her rivals.

“My serve, it can be a really good weapon and I’m not doing as much running from the baseline,” 30-year-old Plíšková said.

Plíšková will play Zhang Shuai on Monday for a place in the quarterfinals after China’s 23rd seed ended the run of American qualifier Katie Volynets 6-3, 6-2.

Belinda Bencic, who opened the season with success at the Adelaide International 2, also advanced after extending her winning streak to eight matches with a 6-2, 7-5 victory over Camila Giorgi.

The Swiss world number 10 faces Adelaide International 1 champion Aryna Sabalenka next in a test of both their Australian Open title credentials.

Fifth-seeded Sabalenka outclassed Belgian Elise Mertens 6-2, 6-3 to rack up her seventh successive straight-sets victory of the year.

“That’s a great stat but I’m just focused on myself, trying to keep it up,” the Belarusian said.

Croatia’s Donna Vekić also progressed to the fourth round on day five, matching her effort from 2021, with a 6-2, 6-2 disposal of Spaniard Nuria Parrizas Diaz.

On Monday, Vekic will play unseeded Linda Fruhvirtova after the teenage sensation took out Czech compatriot and French Open finalist Markéta Vondroušová 7-5, 2-6, 6-3.

AAP