Spain's Roberto Bautista Agut (36) came from behind to defeat Hungary's Fabian Marozsan (25) 3-6, 6-3, 7-6 (4), in the only three-set match of the day.
Winning in straight sets were Alexei Popyrin (25) of Australia, Russia's Karen Khachanov (28), Zizou Bergs (25) of Belgium and Giovanni Mpetshi Perricard (21) of France.
Movistar Chile Open
Cristian Garin (28) gave his hometown fans something to cheer about, rallying for a 2-6, 6-4, 6-4 win over Argentine qualifier Juan Pablo Ficovich (28) in the first round at Santiago, Chile.
Garin took advantage of just three of his 16 break-point opportunities, but he wound up with a 9-3 edge in aces.
In other opening-round action, qualifier Gustavo Heide (22) downed Thiago Seyboth Wild (24) 7-5, 6-2 in an all-Brazilian matchup. Germany's Yannick Hanfmann (33) topped Argentina's Facundo Diaz Acosta (24) 7-5, 6-3, and Serbia's Laslo Djere (29) eliminated Peru's Ignacio Buse (20) 6-4, 6-3.