Players seeded fifth through eighth have survived to play in Saturday's semifinals.
Potito Starace, who is the highest seed left at No. 5, advanced by downing Horacio Zeballos 6-7 (9-11), 6-3, 7-6 (7-2).
Santiago Giraldo will meet Starace in the semifinals after ousting fourth-seeded Ignacio Chela 6-4, 6-3.
This week begins the series of clay-court events that will lead up to the French Open, the second major championship of the season.