Novak Djokovic and Rafael Nadal were largely untroubled in their openers at the Abierto Mexicano Telcel on Tuesday.
Djokovic, the top seed who accepted a wildcard into the ATP 500 event, was too good for Martin Klizan 6-3 7-6 (7-4).
The Serbian world number two broke serve three times during his win, which set up a second-round clash with Juan Martin del Potro.
Del Potro fought his way past American teenager Frances Tiafoe 6-4 3-6 7-6 (7-1), and his meeting with Djokovic will be their first since the Argentinian's stunning win at the Rio Olympics.
Nadal, playing for the first time since losing the Australian Open final, also did it easily, breezing past Mischa Zverev 6-4 6-3.
The Spaniard is a two-time champion in Acapulco and had few problems beating Zverev for the second time this year.
Nadal's next opponent is Paolo Lorenzi after the Italian edged Lu Yen-hsun 4-6 6-3 6-4.
Fellow seeds Marin Cilic, Dominic Thiem and Nick Kyrgios also advanced to the second round.
Cilic lost just nine third-set points in a 6-3 4-6 6-0 win over wildcard Alexandr Dolgopolov.
Thiem, the defending champion, extended his winning streak to six with a 7-6 (9-7) 6-3 victory against Gilles Simon, while Kyrgios beat Dudi Sela 3-6 6-3 6-3.
Kyrgios' fellow Australian Bernard Tomic saw his poor form continue, last year's runner-up retiring after dropping the first set 7-6 (7-5) to Donald Young.
Jack Sock, coming off a title win in Delray Beach, was the only seed to depart, going down to qualifier Yoshihito Nishioka 3-6 6-2 6-1.
American Sam Querrey needed almost two hours to overcome Kyle Edmund 6-2 4-6 6-3.
At the Brasil Open, seeds Fabio Fognini, Diego Schwartzman, Federico Delbonis and Carlos Berlocq reached the second round.