Singapore - Second-seeded Garbine Muguruza improved to 2-0 in group-stage matches at the WTA Finals by beating Angelique Kerber 6-4, 6-4 Wednesday.
In the day's other match, fourth-seeded Petra Kvitova defeated fellow Czech Lucie Safarova 7-5, 7-5 for her first win in Singapore.
Muguruza broke Kerber twice in each set to wrap up the win in 1 hour, 38 minutes.
Kvitova improved to 8-0 in career matches against the ninth-seeded Safarova, who fell to 0-2 in her first appearance at the season-ending tournament. Kvitova and Kerber are 1-1, with all four still in contention for a spot in the semi-finals.