Roger Federer, of Switzerland, reacts after winning the first set over Kevin Anderson, of South Africa, in the quarterfinals of the BNP Paribas Open tennis tournament, Thursday, March 13, 2014, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Kevin Anderson, of South Africa, returns a shot to Roger Federer, of Switzerland, during the quarterfinals of the BNP Paribas Open tennis tournament, Thursday, March 13, 2014, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Roger Federer, of Switzerland, serves to Kevin Anderson, of South Africa, during their quarterfinal match at the BNP Paribas Open tennis tournament on Thursday, March 13, 2014, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Sloane Stephens smiles prior to serving to Flavia Pennetta, of Italy, during a quarterfinal match at the BNP Paribas Open tennis tournament, Thursday, March 13, 2014, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Sloane Stephens, of the United States, serves to Flavia Pennetta, of Italy, during a quarterfinal at the BNP Paribas Open tennis tournament, Thursday, March 13, 2014 in Indian Wells, Calif. (AP Photo/Mark J. Terrill)
Sloane Stephens hits to Flavia Pennetta, of Italy, during a quarterfinal match at the BNP Paribas Open tennis tournament Thursday, March 13, 2014, in Indian Wells, Calif. (AP Photo/Mark J. Terrill)