Angelique Kerber of Germany returns a shot to Serena Williams of the USA during their tennis match at the WTA championship in Istanbul, Turkey, Tuesday, Oct. 23, 2012. (AP Photo)

 

              Angelique Kerber of Germany returns a shot to Serena Williams of the USA during their tennis match at the WTA championship in Istanbul, Turkey, Tuesday, Oct. 23, 2012. (AP Photo)
Angelique Kerber of Germany returns a shot to Serena Williams of the USA during their tennis match at the WTA championship in Istanbul, Turkey, Tuesday, Oct. 23, 2012. (AP Photo)
Tags: Germany , USA