Serena Williams has beaten Angelique Kerber in straight sets in her opening match of the WTA Championships in Istanbul.
The American world number one is aiming to win the end-of-season tournament for the third time in her career.
Williams broke early in the opening set before saving two break points on her way to closing it out 6-3 in routine fashion.
A lengthy game at the start of the second saw Williams break again, and she had little trouble seeing off the German world number nine 6-1 with just over an hour on the clock.
