Victoria Azarenka looks favoured to end the year as world No. 1 but few of the eight women who qualified for this week's season-ending WTA Championships would argue that Serena Williams still rules the roost.
Williams, the 30-year-old American ranked third in the world, won the last two grand slams of the season, either side of claiming singles and doubles gold at the Olympics.
She has not played a match since beating Azarenka to win her 15th grand slam title at Flushing Meadows but will be recharged for the start of the Championships in Istanbul today, where Williams faces Azarenka, China's Li Na and German Angelique Kerber in round-robin action.
The other group features last year's season-ending champion Petra Kvitova, Maria Sharapova, Sara Errani and Agnieszka Radwanska.
