Ferrer joins fellow-Spaniard Tommy Robredo in the final eight after the No. 4 seed downed Dusan Lajovic of Serbia 6-2, 6-1 in the outdoor clay tournament. Eleven of Robredo's 12 ATP titles have been won on clay.
Ferrer next faces Brazil's Thomaz Bellucci, who came back to claim an upset 4-6, 6-3, 6-3 win over No. 7 seed Juan Monaco (7), Argentina.
In women's matches at the joint WTA-ATP event, top-seeded Klara Zakopalova of the Czech Republic beat Spain's Silvia Soler-Espinosa 6-4, 6-1 to reach the quarterfinals.
Third-seeded Paula Ormaechea of Argentina defeated Dutchwoman Kiki Bertens 7-5, 7-5 to also land in the quarterfinals.
No. 5 Kurumi Nara of Japan beat Taiwan's Hsieh Su-wei 6-3, 6-2 to reach the second round. Anna-Lena Friedsam of Germany is also into the second round, while Poland's Katarzyna Piter and Nastassja Burnett of Italy won to advance to the quarterfinals.