Philipp Kohlschreiber began his quest for a second Heineken Open title in Auckland on Tuesday with a hard-fought victory over Swiss qualifier Stephane Bohli.
The German eighth seed won the tournament in 2008 and looked sluggish on centre court, later admitting that he was suffering from jet lag.
Kohlschreiber eventually won 6-4 4-6 6-4.
Frenchman Adrian Mannarino's impressive form continued with the qualifier upsetting fifth seed Kevin Anderson 6-3 6-3 in their first round match.
Mannarino made it all the way to the quarter-finals at last year's tournament, but had to beat New Zealand No 2 Artem Sitak in Monday's qualifying final to advance to this year's main draw.
Ryan Harrison beat fellow American Sam Querrey 6-4 6-3.