Fourth-seeded Monica Puig topped Daniela Hantuchova 6-4, 6-4 to advance to the quarterfinals of the Abierto Mexicano Telcel on Wednesday.
Puig, from Puerto Rico, shook off a slow start in the opening set, unable to convert two set points while fighting off two breaks. But a booming ace won the first set, and she cruised in the second.
Puig had a chance to put away Hantuchova with three match points, but the Slovakian fought her off five times before succumbing.
Puig will take on Christina McHale for a spot in the semifinals after the American knocked out her countrywoman Taylor Townsend 6-1, 7-6 (5) earlier in the day.
Kirsten Flipkens of Belgium knocked off Ajla Tomljanovic of Croatia, who retired after dropping the first set 7-5. No. 7 seed Lesia Tsurenko of Ukraine advanced over Germany's Julia Goerges, who retired down 2-0 in the second set after dropping the first.