Alexandr Dolgopolov and Jeremy Chardy bowed out in the first round of the inaugural Abierto Mexicano Los Cabos, but Nicolas Almagro and Marcel Granollers advanced.
Dolgopolov was the biggest casualty on Tuesday after wet weather washed out play 24 hours earlier, with the Ukrainian fifth seed stunned 6-3 6-3 by Horacio Zeballos.
In a contest lasting a little over an hour, Dolgopolov tallied four double faults and was broken as many times in a lacklustre display against the Argentinian at the ATP 250 event.
"I don't think I played really solid today," Dolgopolov said. "I was missing a lot. He just played better than me."
Zeballos will face Julien Benneteau in the second round after the Frenchman outlasted Jared Donaldson 4-6 7-6 (7-4) 6-2.
French seventh seed Jeremy Chardy also made a first-round exit, beaten 6-4 7-6 (8-6) by Pablo Carreno Busta, who earned a meeting with Austin Krajicek.
Krajicek accounted for Mexican wildcard Tigre Hank 7-6 (7-2) 6-3.
Nicolas Almagro - Spain's seventh seed - battled past Noah Rubin 6-2 3-6 6-3.
Spanish eighth seed Granollers fared much better in the opening round, seeing off countryman Fernando Verdasco 7-6 (7-2) 6-2.
Granollers dominated on serve, dropping just six points on his first serve, while converting three of 15 break points.
Next up for Granollers is Tobias Kamke, who prevailed 2-6 6-2 6-0 against Tim Smyczek.
In other results, Santiago Giraldo defeated Amir Weintraub 6-4 6-4, in-form Reilly Opelka benefited from a retirement to triumph 7-6 (8-6) 3-1 against Sergiy Stakhovsky, Adrian Mannarino fell to Mischa Zverev 6-1 6-1, Dusan Lajovic dispatched Thiago Monteiro 6-3 6-4 and Guillermo Garcia-Lopez made light work of Lucas Gomez 6-0 6-1.