Williams beats Azarenka at WTA Championships

Serena Williams beat world number one Victoria Azarenka in straight sets as Sara Errani defeated Samantha Stosur in Istanbul, Turkey yesterday.

Williams has an 11-1 career record against Azarenka and has won the last nine matches between the two.

The American is predicted to finish the tournament as world number three, regardless of her finish at the season closer.

In the white group, Sara Errani beat Samantha Stosur after dropping the second set, 6-3 2-6 6-0.

Stosur, who replaced defending champion Petra Kvitova, double faulted on match point.

Kvitova withdrew with illness after one match.