Novak Djokovic set up a quarter-final with Japan’s Kei Nishikori at the Tokyo Olympics on Wednesday as gold medal rival Daniil Medvedev struggled with the heat, even asking the chair umpire who would be responsible if he died.

The World No. 1 continued his bid for a calendar Golden Slam by defeating 34th-ranked Alejandro Davidovich Fokina of Spain 6-3, 6-1 to extend his winning run to 21 matches.