Germany's Angelique Kerber celebrates after defeating Madison Keys of the United States in their third-round match at the Australian Open tennis championship in Melbourne, Australia, on Friday, Jan. 18, 2013. (AP Photo/Dita Alangkara)
Venus Williams wipes her face during a match against Angelique Kerber, of Germany, at the U.S. Open tennis tournament on Thursday, Aug. 30, 2012, in New York. (AP Photo/Darron Cummings)
Angelique Kerber reacts after defeating Maria Sharapova 6-4, 6-4 during their quarterfinal singles match at the GDF Suez WTA Open 2012 tennis tournament at Coubertin stadium in Paris on Friday, Feb. 10, 2012. ( AP Photo/Michel Euler)