Australian John Millman has won through to the second round of the ATP event in Mexico with a routine victory over Spaniard Marcel Granollers.
Eighth-seeded Millman won 6-3 6-4 in just 86 minutes.
The world No.44 will next meet German Peter Gojowczyk for a place in the quarter-finals and a potential match-up with American third seed John Isner.
The news was not so good on the opening day for fellow Aussie Jordan Thompson, who was beaten by Frances Tiafoe despite serving 11 aces to the sixth seed's five.
The American won 3-6 6-4 6-3 in a little over two hours to set up a meeting with either Mackenzie McDonald or Emilio Nava.
Three-time Grand Slam champion Stan Wawrinka continued his recent good form with a 6-4 7-6 (8-6) win over Ryan Harrison.
The Swiss lost to Frenchman Gael Monfils in the final of the Rotterdam Open last week and sealed victory in Acapulco with his 26th winner of the night.
Wawrinka faces seventh seed Steve Johnson next, who beat Mexican wild card Gerardo Lopez Villasenor 7-5 7-5.
Australians Nick Kyrgios, Alex de Minaur and Alexei Popyrin will play their first-round matches on Tuesday, as will world number two Rafael Nadal who opens his bid for the title against Mischa Zverev.
