Kevin Anderson and Alexandr Dolgopolov secured first-round wins at the Mexican Open on Monday.
Anderson, runner-up in Acapulco last year, had no problems in a 6-1 6-2 thrashing of German Dustin Brown.
The fourth seed was completely untroubled, losing just eight points on serve on his way to victory in 52 minutes at the ATP 500 event played on hard courts.
South African Anderson will face either Croatian Ivan Dodig or American Steve Johnson in the second round.
It was a good day for the seeds, with Dolgopolov also among the winners.
The Ukrainian fifth seed lost just six points in the third set of a 6-3 4-6 6-0 victory over Australian Sam Groth.
Awaiting Dolgopolov in the second round is either Dutchman Robin Haase or Austrian Andreas Haider-Maurer.
Like Anderson, Santiago Giraldo got a wildcard in Mexico and the seventh seed made a winning start with a 7-6 (10-8) 6-1 victory over American qualifier Austin Krajicek.
The Colombian came from a break down and saved two set points in the first set.
The eighth-seeded Benjamin Becker also advanced, winning an all-German affair against Tobias Kamke 7-6 (7-4) 6-2.
There were also wins for Marinko Matosevic and Dusan Lajovic.
Australian Matosevic cruised past Marcel Granollers 6-4 6-2 and Lajovic overcame qualifier Thanasi Kokkinakis 6-4 7-6 (7-4).