Top seed Caroline Wozniacki cruised through to the second round of the WTA Auckland Classic on Tuesday but other seeded players struggled in their opening matches of the new year.
The third and fourth seeds Barbora Strycova and Agnieszka Radwanska were both pushed to three sets, as was number two seed Julia Goerges on the rain-disrupted previous day.
The other four seeds, including defending champion and fifth seed Lauren Davis, were all eliminated in the first round.
But there were no problems for Wozniacki after the Dane recovered from a rough start to romp home 6-3, 6-0 against American Madison Brengle.
"I didn`t really know what to expect. It was my first match back and I hit some crazy shots in those first few games and I thought `Wow, this is going well` and then I`d make an easy mistake straight after," she said.
"I kind of found my ground as the match progressed and started being more steady and going for my shots when I found the opportunity."
Radwanska scraped through to the second round in a tough three-setter against Brazilian Beatriz Haddad Maia.
The Pole was down a break in the third set before rallying to beat the 21-year-old 6-2, 4-6, 6-2.
"The most important thing, I won the third set," she said.
"This is the first tournament of the year, so we don`t know how the girls are playing and you`ve got to start from the beginning.
"So I think there`s less pressure after the first match."
It took Strycova three hours to beat Italian Sara Errani 6-4, 6-7 (3-7), 6-4, with the Czech not fully showing her class until the last game when Errani was broken to love.
Defending champion Davis was bundled out 6-1, 6-2 by fellow American Sachia Vickery, who only made the main draw after going through qualifying without dropping a set.
Another qualifier, Ysaline Bonaventure from Belgium, knocked out sixth seed Yulia Putintseva from Kazakhstan 6-3, 6-3. Seventh seed Mona Barthel of Germany also went out in straight sets, losing 6-2, 6-2 to American Varvara Lepchenko.