Benoit Paire held off a fighting challenge from rising star Jannik Sinner to move into the second round of the Auckland Open, while top seed Alex de Minaur withdrew from the Adelaide International.
At the first edition of the ATP tournament in Adelaide, sixth seed Cristian Garin fell to Lloyd Harris, the South African qualifier winning 7-6 (7-5) 3-6 6-4.
Jeremy Chardy defeated fellow Frenchman Gilles Simon in straight sets, with Dan Evans, Sam Querrey and home hope James Duckworth the other players to progress.
The action came as top seed De Minaur pulled out of the event after aggravating an abdominal injury while representing Australia at the ATP Cup.
"I have seen the physios, I have seen the doctors and I will be continuing to do that for the whole of the week and hopefully I will be ready to play in Melbourne," De Minaur said ahead of the Australian Open.
In Auckland, Italian Sinner – winner of the Next Generation ATP Finals in November – took number five seed Paire to a final set but the Frenchman eventually prevailed 6-4 2-6 6-4 in one hour and 55 minutes.
Defending champion Tennys Sandgren started his campaign with a routine 6-4 6-3 triumph over wildcard Michael Venus.
But last year's beaten finalist Cameron Norrie was knocked out in straight sets by qualifier Thiago Monteiro, with American Frances Tiafoe also being eliminated at the hands of qualifier Mikael Ymer.
Hubert Hurkacz and Ugo Humbert saw off Lorenzo Sonego and Casper Ruud respectively in Monday's other matches.