Caroline Wozniacki and Venus Williams strolled into the quarter-finals of the Auckland Classic on Wednesday with second-round straight-sets wins.
Venus Williams was made to work at the start of her match with Japan's fleet-footed Kurumi Nara, dropping serve twice before shifting up a gear to cruise home 6-4, 6-1.
Although the win was comfortable, 34-year-old Williams was not satisfied with the way her usually venomous serve misfired, delivering a less than 50 percent success rate.
She plays Russian Elena Vesnina in the quarter-finals after the Russian breezed past Croatian teenager Ana Konjuh 6-3, 6-1.
Head-to-head, Vesnina leads Williams 2-1 although Williams won their last encounter in Dubai 11 months ago.
The pressure was reversed for top-seed Caroline Wozniacki who cruised through the first set against rising American Taylor Townsend and then struggled to get home in two sets 6-1, 7-6 (7-4).
Wozniacki's first serve worked a treat with an 81 per cent success rate and no double faults, but she had difficulty dealing with Townsend's switch to go to the net more in the second set.
The left-handed American broke serve to lead 4-2 in the second set but double-faulted when serving for the set, and Wozniacki came through to close out the tiebreak with an ace.
"The second set I broke her and thought it's going well for me and all of a sudden I see myself down 5-2 and she started playing really well. All of a sudden I had to fight my way back," Wozniacki said.
Of the other seeded players still alive, seventh seed Coco Vandeweghe beat last year's semi finalist Kirsten Flipkens of Belgium 6-1, 6-7 (7-5), 7-5 while in an all-American clash Lauren Davis disposed of sixth seed Sloane Stephens 1-6, 6-4, 6-1.