Serena Williams starts defense of WTA Championship title with win over ATP Tour 500 . World No.2 Victoria Azarenka also a winner on Tuesday beating Sara Errani 7-6 , 6-3 -2 . Stanislas Wawrinka crashes out of home Angelique Kerber event in Stanislas , Basel .
Serena Williams starts defense of WTA Championship title with win over Angelique Kerber . World No.2 Victoria Azarenka also a winner on Tuesday beating Sara Errani 7-6 , 6-2 . Stanislas Wawrinka crashes out of home ATP Tour 500 event in Basel , Switzerland .