Serena Williams of the U.S. returns the ball to Alize Cornet of France during a semi final match of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Friday, Feb. 21, 2014. (AP Photo/Kamran Jebreili)
Alize Cornet of France celebrates after she beats Serena Williams of the U.S. during a semi final match of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Friday, Feb. 21, 2014. (AP Photo/Kamran Jebreili)
Alize Cornet of France serves the ball to Serena Williams of the U.S. during a semi final match of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Friday, Feb. 21, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. clenches a fist in a match against Jelena Jankovic of Serbia during the quarterfinals of the Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Thursday, Feb. 20, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. returns the ball to Jelena Jankovic of Serbia during the quarterfinals of the Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Thursday, Feb. 20, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. returns the ball to Ekaterina Makarova of Russia during the second round of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Tuesday, Feb. 18, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. reacts in a match against Ekaterina Makarova of Russia during the second round of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Tuesday, Feb. 18, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. returns the ball to Ekaterina Makarova of Russia during the second round of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Tuesday, Feb. 18, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. reacts after winning a point against Ekaterina Makarova of Russia during the second round of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Tuesday, Feb. 18, 2014. (AP Photo/Kamran Jebreili)
Serena Williams of the U.S. watches her sister Venus, unseen, in a match against Elena Vesnina of Russia during the first round of Dubai Duty Free Tennis Championships in Dubai, United Arab Emirates, Monday, Feb. 17, 2014. (AP Photo/Kamran Jebreili)