Ashleigh Barty of Australia serves to Serena Williams of the U.S. during the first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)
Serena Williams of the United States hits a forehand return to Ashleigh Barty of Australia during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Aaron Favila)
Serena Williams of the United States hits a forehand return to Ashleigh Barty of Australia during their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Aaron Favila)
Serena Williams of the United States stretches for a return to Ashleigh Barty of Australia at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014.(AP Photo/Eugene Hoshiko)
Novak Djokovic of Serbia celebrates after defeating Lukas Lacko of Slovakia in their first round match at the Australian Open tennis championship in Melbourne, Australia, Monday, Jan. 13, 2014..(AP Photo/Aaron Favila)