Rafael Nadal, playing in his third tournament in four weeks after his lengthy layoff, needed one hour and 16 minutes to get past Argentine qualifier Martin Alund 6-0, 6-4.
Nadal pocketed the first set in less than half an hour, saving all three of the break points he faced in the contest and winning 26 of his 33 first service points.
The convincing victory came a fortnight after Nadal needed three sets to get past Alund in the semi-finals of the clay court tournament in Sao Paulo, where Nadal went on to win his first title since last year's French Open.
A week before that he fell in the final at Vina del Mar in Chile to Horacio Zeballos.
"The first set I played at a very high level," Nadal said. "I started strong without any errors. In the second set Martin played at a high level and made it hard to close it out.
"I'm happy to be in the quarter-finals."
The relatively low-key clay court tournaments in Latin America were expected to serve as Nadal's preparation for prestigious Masters Series events on US hard courts at Indian Wells, California, and Miami.
Nadal has denied a Spanish media report that he has already decided to skip Indian Wells and Miami, saying he intended to go to Indian Wells and would only opt out if he feels his troublesome left knee is not up to it.
Men's main draw play begins at Indian Wells on March 7.
At both Vina del Mar and Sao Paulo, Nadal was the top seed but in Acapulco he is seeded second behind fellow Spaniard David Ferrer.
At number four in the world, Ferrer is currently ranked one spot higher than former number one Nadal and is the three-time defending champion in Acapulco.
Ferrer and defending women's champion Sara Errani also booked their quarter-final berths in this combined ATP and WTA event on Wednesday.
Thirty-year-old Ferrer defeated US qualifier Wayne Odesnik 6-2, 6-1, while Italy's Errani defeated Canada's Eugenie Bouchard 7-6 (7/4), 6-2.
Men's third seed Nicolas Almagro of Spain also advanced, rallying in the second set to finish off a 6-4, 7-6 (7/4) victory over compatriot Tommy Robredo.
Ferrer arrived in Acapulco fresh from a victory on Sunday at Buenos Aires.
Last season he won both the Buenos Aires and Acapulco titles to kick-start a season that included an ATP tour-leading seven titles.
Ferrer next faces Italian Paolo Lorenzi, a 6-4, 6-3 winner over Spain's Pablo Andujar.
Nadal, seeking a 38th career clay court title, will face Argentina's Leonardo Mayer in the quarter-finals. Mayer defeated Russian Andrey Kuznetsov 6-2, 6-2.
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