Defending champion Agnieszka Radwanska lost her first match of the WTA Finals in Singapore, with Svetlana Kuznetsova surviving match point to score the upset.

Dinara Safina was forced to withdraw from the season-ending Sony Ericsson Championships in Doha with a back injury last night, leaving Serena Williams to end 2009 as the world's number one - a feat the American celebrated with a defeat of her sister Venus.