Caroline Wozniacki celebrated in defeat on Wednesday after injured Russian Maria Sharapova's withdrawal from the season-ending WTA Championships made sure the Dane would end the year as World No 1.
Serena Williams capped off a season to remember by capturing her fourth WTA Championship title with a 2-6, 6-3, 6-0 win over Li Na on Sunday.
China's Li Na made it a hat-trick of White Group victories, overpowering back-injury victim Victoria Azarenka 6-2, 6-1 on Friday to march through to the semi-finals of the WTA Championship.
World No 1 Serena Williams showed her determination to defend her WTA Championships title by sweeping to a 6-3, 6-1 win over Angelique Kerber at the season-ending event on Tuesday.
Round-robin formats at tennis tournaments can cause confusion but Serena Williams has an easy solution, just keep winning.
World No 1 Serena Williams beat Agnieszka Radwanska for the eighth time in eight matches to move ominously towards the semi-finals of the WTA Championships on Wednesday.
China's Li Na will meet Serena Williams in the final of the WTA championships after beating Czech Petra Kvitova 6-4, 6-2 on Saturday, becoming the highest-ranked player ever from an Asian country.