Garbine Muguruza reached the WTA Finals last four unbeaten on Friday after a tough win over Petra Kvitova — who also qualified for the semis with help from her fellow Czech Lucie Safarova. On a rollercoaster last day of group play, Muguruza and Kvitova shared 15 service breaks in a see-sawing three-setter before the increasingly impressive Spaniard won 6-4, 4-6, 7-5. Kvitova’s hopes were hanging by a thread but she went through when her friend and Fed Cup teammate Safarova beat Angelique Kerber 6-4, 6-3, stopping the German finishing second in White Group.