Sixth seed Feliciano Lopez recovered from a set down to beat wildcard Michael Venus in the first round of the ASB Classic, while Philipp Kohlschreiber was a straight-sets winner against Fabio Fognini in the Sydney International.
Lopez was a strong favourite to see off Venus in Auckland, but the Spaniard made hard work of defeating the home favourite 3-6 6-4 6-3.
He frustrated the doubles specialist by saving six of seven break points and earned the decisive break in what proved to be the penultimate game of the match to reach round two.
Steve Johnson needed just the two sets to advance at the expense of Stephane Robert, who won only three points on the seventh-seeded American's serve as he was beaten 6-4 6-3.
Jiri Vesely, Malek Jaziri, Robin Haase and Dustin Brown also progressed.
Kohlschreiber was given a testing draw in the opening round in Sydney, but the fifth seed prevailed 6-4 6-4.
The German was broken for the only time in the match in the first game, but bossed the baseline rallies and was impressive on serve in the second set as he made it through.
Australian qualifier Matthew Barton upset the odds to dump out Kyle Edmund, winning 7-6 (7-3) 7-6 (7-5) in a contest during which neither player managed a break of serve.
Paolo Lorenzi, Dan Evans and Gastao Elias all enjoyed first-round success on Monday.