Karolina Pliskova was the first player to secure a last-eight spot at the WTA Brisbane International, with fellow seed eventually Garbine Muguruza battling through to join her.
The Czech, seeded third, was a dominant 6-1 6-4 winner over Asia Muhammad on Tuesday, in stark contrast to Muguruza's latest epic in Australia.
Having needed three sets to see off home favourite Sam Stosur in the opening round, fourth seed Muguruza again had her work cut out against Daria Kasatkina, ultimately prevailing 7-5 3-6 7-6 (9-7).
The world number seven was 6-5 down in the decider after surrendering her one-set advantage, but the French Open champion dug deep again to triumph in just over three hours.
Sixth seed Elina Svitolina also had to show her grit in a 7-5 2-6 7-5 win over Shelby Rogers, with Alize Cornet through following a 6-2 6-1 victory over Christina McHale.
In a rain-affected first-round match, 16-year-old Destanee Aiava upset the odds to defeat Bethanie Mattek-Sands 2-6 6-3 6-4.