It was a mixed day for seeds at the Abierto Mexicano Telcel as Kevin Anderson eased to victory after John Isner was eliminated.
Flying high after winning the New York Open, Anderson continued his fine form by accounting for Radu Albot 6-4 6-3 on Monday.
The fifth seed relied on his serve in Acapulco, firing down 11 aces, while winning 88 per cent of his first serves against the Moldovan.
South Africa's Anderson will face either Adrian Mannarino or Ricardas Berankis in the second round.
Big-serving American and eighth seed Isner fell at the first hurdle at the ATP 250 tournament, which is headlined by 16-time grand slam champion Rafael Nadal.
Isner succumbed to countryman Ryan Harrison 6-3 7-6 (7-5) on the Mexican hard courts.
There was some revenge for four-time winner David Ferrer, who defeated Andrey Rublev 6-4 6-3.
Rublev upstaged Ferrer at the Australian Open last month but the Spanish veteran avoided another loss to the 20-year-old.
As for Jared Donaldson, he was leading 6-3 3-2 when Nikoloz Basilashvili retired.
Meanwhile, Federico Delbonis and Leonardo Mayer advanced at the Brasil Open.
Delbonis – the 2014 champion and eighth seed – beat Roberto Carballes Baena 6-4 6-4.
Next up is Guillermo Garcia-Lopez, who outlasted Gerald Melzer 6-4 3-6 6-3 on clay in Sao Paulo.
Fifth seed Mayer saved two match points in a 5-7 7-6 (12-10) 7-6 (7-5) victory over Gastao Elias, Carlos Berlocq rallied past Thiago Seyboth Wild 3-6 6-3 6-2, while Joao Domingues prevailed 2-6 7-6 (8-6) 7-5 against Renzo Olivo.
