Spanish veteran Feliciano Lopez scraped through the opening round of the ATP Auckland Classic on Monday after a scare from local wildcard Michael Venus.
With the top-ranked players at the New Zealand tournament given a bye through to the second round, the lesser seeds took centre stage but struggled to dominate.
Lopez, seeded sixth, came from behind to grind out a 3-6, 6-4, 6-3 win over New Zealander Venus, a doubles specialist rated number 1,035 in the singles rankings.
"The match was very close and it could have gone either way," said the Spaniard, who is using the tournament as a warm-up for this month's Australian Open.
American seventh seed Steve Johnson also made a faltering start in his 6-4, 6-3 win over Stephane Robert of France.
Robert, 36, belied his age, attacking the net and chasing down returns. But Johnson eventually wrested control after winning three successive games to take the first set.
"It's tough at the start of the year, you don't have much momentum and you're trying to figure out your game again," said world number 33 Johnson.
"(Robert) came out and played a great return game but I was able to stay in it and just kind of hang around."
Dutchman Robin Haase overcame local hope Finn Tearney 6-4, 7-5 but the world number 58 was also unconvincing.
He fell behind 3-0 in both sets and acknowledged it was only his superior experience in pressure situations that got him through.
"With the wind here, you try to play your game but you have to adjust," he said. "I think I did that a little bit better in the end."
Czech Jiri Vesely, the 2015 champion, ousted Horacio Zeballos of Argentina 6-4, 6-3, while Tunisia's Malak Jaziri advanced with a 7-6 (7/1), 6-3 win over Diego Schwartzman of Argentina.
Germany's Dustin Brown beat Michael Mmoh of the United States 7-6 (7/4), 3-6, 6-4.
The tournament's top four seeds, including four-time winner David Ferrer and defending champion Roberto Bautista Agut, will play in the second round on Wednesday.