Serena Williams

Serena Williams

Serena Williams of the U.S reacts after she returned a shot to Li Na of China during their final tennis match at the WTA Championship in Istanbul, Turkey, Sunday, Oct. 27, 2013. The world’s top female tennis players compete in the championships which runs from Oct. 22 until Oct. 27.(AP Photo)

Serena Williams of the U.S reacts after she returned a shot to Li Na of China during their final tennis match at the WTA Championship in Istanbul, Turkey, Sunday, Oct. 27, 2013. The world’s top female tennis players compete in the championships which runs from Oct. 22 until Oct. 27.(AP Photo)