Former champions Anastasia Pavlyuchenkova and Timea Babos were largely untroubled as they reached the Monterrey Open quarter-finals.
Pavlyuchenkova, a three-time winner of the WTA International event, overcame qualifier Kristie Ahn 7-6 (7-5) 6-4 on Wednesday.
The Russian second seed was on top for the most part before reaching the last eight as she bids for her first crown in Monterrey since 2013.
Pavlyuchenkova will next face 2012 winner Babos, the fifth seed having cruised past Naomi Broady 6-3 6-2.
The Hungarian lost just 11 points on serve against Broady, breaking three times to win in 63 minutes.
French third seed Caroline Garcia, runner-up in 2015, eased into the last eight with a 6-0 6-3 thrashing of qualifier Nadia Podoroska.
Garcia will meet Julia Boserup after the American edged past qualifier Tereza Martincova 6-3 4-6 6-4.