Li Na overcomes Angelique Kerber in Istanbul

Li Na has defeated Angelique Kerber in straight sets at the WTA World Championships in Istanbul.

The world number eight needed just one hour and 25 minutes to dispose of the German 6-4 6-3 to keep her tournament hopes alive.

Kerber was powerless to resist the Chinese player, who was much improved from yesterday's defeat to Serena Williams.

If she is to qualify for the next round, Li must hope that Williams defeats Victoria Azarenka before she faces the Belarusian tomorrow.

The loss brings Kerber's 2012 season to an end.