AP
Switzerland's Roger Federer signs autographs following a practice session at the Australian Open tennis championships in Melbourne, Australia, Saturday, Jan. 27, 2018. Federer will play Croatia's Marin Cilic in the men's singles final on Sunday, Jan. 28, 2018. (AP Photo/Ng Han Guan)
- Ng Han Guan
Switzerland's Roger Federer smiles during a press conference following his semifinal win over South Korea's Hyeon Chung who retired injured at the Australian Open tennis championships in Melbourne, Australia, Friday, Jan. 26, 2018. (AP Photo/Vincent Thian)
- Vincent Thian