"It was an unbelievable match for me."
Earlier, Caroline Wozniacki endured an unexpected struggle against Montenegro's Danka Kovinic. The third seed was broken twice early and found herself 4-0 down in the blink of an eye.
The world No 57 Kovinic, who broke into the top 100 for the first time last year, was going for her shots and not missing much.
"She had nothing to lose, I knew she had a big game and she would go for it and that's normal," said Wozniacki. "I remember myself when I was younger, that was [the approach I took]."
But the Dane showed the grit that has characterised her career, winning the next six games to take the first set 6-4. Wozniacki also came up with one of the shots of the day to force set point, scooping a well-placed Kovinic drop shot from an almost impossible angle for a winner.
Wozniacki was more confident in the second set and, despite some admirable resistance from the 21-year-old Kovinic, closed out the match 6-4 6-4 in under 90 minutes.
She is an amazing tennis player and I respect her so much. It was an unbelievable match for me.
The first match on centre court - meant to be an entree before the big three - was a pearler, as Italian veteran Francesca Schiavone and Austrian Tamira Pascek duelled for almost three hours. The 35-year-old Schiavone fought gamely and produced some wonderful shots but was eventually beaten by Pascek 7-6 (3) 4-6 6-3 in two hours and 49 minutes.
On the outside courts, Czech veteran Barbora Strycova beat Dutch qualifier Kiki Bertens 6-2 6-4. The 2015 ASB Classic semifinalist Strycova is one of the cleanest strikers of the ball and was relatively untroubled against the world No 104.
In other matches, Auckland favourite Julia Goerges beat Czech Lucie Hradecka 6-0 6-3. The German hit seven aces and didn't give up a break point in a dominant display.
Others to advance were American world No 63 Christina McHale, who strolled past Japan's Misaki Doi 6-2 6-4, and 2013 semifinalist Kirsten Flipkens, who trumped American Bethanie Mattek-Sands 3-6 6-4 6-3.