Britain's Heather Watson swept aside sixth seed Ekaterina Makarova as she continued the defence of her Monterrey Open title.
Watson, 24, triumphed 6-4 6-1 over the world number 45 to set up a quarter-final with top seed Angelique Kerber.
World number 125 Watson broke in the 10th game of the opening set then did so again twice in the second before converting her sixth match point.
Kerber progressed by beating Mandy Minella of Luxembourg 6-1 6-3.
British number three Watson began her defence of the title by beating Serbia's Nina Stojanovic 6-2 6-7 (7-9) 6-4 on Wednesday.