Sixth seed Petra Kvitova had a good head-to-head record going into her match against Poland 's Agnieszka Radwanska and once again came out on top . Serena Williams starts defense of WTA Championship title with win over Angelique Kerber . The world No. 1 won 6-3, 6-2 in just under two hours to claim the title. Stanislas Wawrinka crashes out of home ATP Tour 500 event in Basel , Switzerland .
Serena Williams starts defense of WTA Championship title with win over Angelique Kerber . The world No. 1 won 6-3, 6-2 in just under two hours to claim the title. Stanislas Wawrinka crashes out of home ATP Tour 500 event in Basel , Switzerland .