Major drawcards Caroline Wozniacki and Venus Williams overcame some tricky moments to make safe passage into the ASB Classic quarter-finals.

Top seed Wozniacki came from behind in the second set to beat American wildcard Taylor Townsend 6-1 7-6 (7-4) on Wednesday in Auckland.

On the other side of the draw, third seed Williams put a sluggish start behind her to ease past Japan’s Kurumi Nara 6-4 6-1.

Townsend, 18, mixed errors and winners as she dropped the opening set.

Having been broken early in the second, the world No.103 hit back with two breaks of her own to lead 5-2, but showed signs of nerves in failing to serve out the set.

Wozniacki held the upper hand through most of the tiebreaker, which the Dane closed out with an ace.

“It was a big grind, but I played really well and I thought Taylor did too,” she said.

“I was a bit lucky I got the set points, but it was great to get another match like this.”

The world No.8 will next face unseeded German Julia Goerges, who beat Czech qualifier Lucie Hradecka 6-3 7-5.

Wozniacki and Georges have split their six previous meetings.

Williams’ opening set against Nara was a tight one, with both players having problems holding serve.

In the second, the 34-year-old American found her rhythm and reeled off the last six games.

“I think I just got my bearings a little bit,” she said.

“Also, I haven’t played her so often so I just had to understand her game a little a bit.”

The seven-time grand slam champion and Classic runner-up last year gave credit to an opponent over whom she had a distinct height advantage.

“She’s tenacious and she understands how to construct points,” she said.

Even so, the contest took just 65 minutes, meaning Williams has been on court for less than two hours over the first two rounds.

Her quarter-final adversary is Elena Vesnina, who raced through her clash with Croatia’s Ana Konjuh.

The Russian, a regular visitor to Auckland and a finalist six years ago, was always in control against her 17-year-old opponent to win 6-3 6-1.

Vesnina has a 2-1 head-to-head advantage over Williams.

Their first encounter came in the opening round at Wimbledon in 2012, and the 28-year-old Vesnina described her 6-1 6-3 win then as still the biggest of her career.

“It’s going to be a difficult match for me and I’m just looking forward to it because she’s a legend,” she said.

The last eight features a qualifier in Poland’s Urszula Radwanska, who downed unseeded Slovakian Daniela Hantuchova 1-6 6-3 6-1.

The match was the durable Radwanska’s fifth of the week, all of which have gone to three sets.