Minella edged past Arantxa Parra Santonja 2-6, 6-3, 6-2 with three breaks in each the second and third sets.
Parra Santonja dominated the first set, losing only five points on serve but Minella took more than 56 percent of the points when receiving serve and won six of her seven break-point chances.
Arruabarrena-Vecino rolled by Chiara Scholl 6-2, 6-0. She won 60 percent of the points in the match and had seven breaks. Scholl's two game wins were both breaks but Arruabarrena-Vecino won nearly two-thirds of the points off Scholl's serve.
Fourth-seeded Alexandra Panova beat Masa Zec-Peskiric 6-3, 6-2 but Sharon Fishman routed No. 8-seeded Tatjana Malek with six breaks in seven games.
Also Tuesday, Julia Cohen beat Grace Min 6-2, 6-1; Sesil Karatantcheva just got by Stephanie DuBois 4-6, 6-4, 7-6 (7-5); Catalina Castano stopped Ines Ferrer Suarez 6-1, 6-3; Estrella Cabeza Candela defeated Kateryna Kozlova 6-4, 6-3; and Eugenie Bouchard was a 7-5, 6-2 winner over Laura Thorpe.
'SNL': 'Anchorman 2' cast, One Direction sing 'Afternoon Delight' [VIDEO]
Exploding whale video goes viral on Internet