FILE - In this Jan. 28, 2016, file photo, Roger Federer, left, of Switzerland and Novak Djokovic, right, of Serbia, pose for a photo ahead of their semifinal match at the Australian Open tennis championships in Melbourne, Australia. The pair will team up for the first time when they take on Jack Sock and Kevin Anderson in doubles on the first day of the second edition of the Laver Cup on Friday in Chicago. (AP Photo/Aaron Favila, File)