Florianopolis, Brazil (SportsNetwork.com) - Top seed Carla Suarez Navarro was a quarterfinal winner Thursday at the Brasil Tennis Cup.

The Spaniard was leading 4-1 in the third set against Monica Niculescu when the reigning Florianopolis champion retired.

The fifth-seeded Romanian claimed the first set 6-4 before Suarez Navarro rallied to take the second set 6-0. Niculescu was broken in her final five service games.

Up next for Suarez Navarro will be Klara Zakopalova. The third-seeded Czech also landed in the final four via a retirement. Zakopalova, who was last week's runner-up in Rio de Janeiro, was leading 6-3, 5-2 when Romanian qualifier Alexandra Dulgheru called it quits.

Friday's other semifinal will pit Spain's Garbine Muguruza against Kazakhstan's Yaroslava Shvedova. The second-seeded Muguruza outlasted Belgian qualifier Alison Van Uytvanck 6-2, 6-7 (1-7), 6-3 and Shvedova ousted sixth- seeded Romanian Alexandra Cadantu 6-3, 6-3.