Muguruza ousted second-seeded Kirsten Flipkens 6-4, 6-3 with a total of five breaks. Muguruza won more than half (34-of-65) of the points when Flipkens served and was able to finish off five of her 17 break opportunities.
She needed 11 break chances to get two first-set breaks and was 3-of-6 in those situations to finish off the win.
Cabeza Candela defeated Monica Niculescu 3-6, 7-6 (7-3), 6-4 in 2 hours, 40 minutes. Niculescu was 6-for-6 in her break chances but Cabeza Candela had three breaks in the second set and two more in the third to gain the semifinals.
Also Thursday, top-seed Samantha Stosur beat eighth-seeded Bojana Jovanovski 6-3, 6-2 with two breaks in each set and No. 7-seeded Klara Zakopalova was a 6-4, 7-5 winner over Alison Riske with three breaks in each set.
Stosur takes a 3-1 career edge over Zakopalova in their semifinal. They have seven titles and 31 WTA finals appearances between them. Neither Muguruza nor Cabeza Candela has previously advanced to a WTA championship match. Cabeza holds a 2-1 series advantage over Muguruza.