Top-seeded Daniil Medvedev hobbled into the fourth round of the Miami Open on Sunday with a gritty 7-6 (7/3), 6-7 (7/9), 6-4 victory over Alexei Popyrin. World No. 2 Medvedev, who appeared to be fighting leg cramps as the match wore on in the heat and humidity of South Florida, nevertheless mustered the only service break of the third set on the way to a dramatic victory over 86th-ranked Popyrin of Australia. The Russian, runner-up to Novak Djokovic at the Australian Open in February, will face either 16th-seeded Dusan Lajovic of Serbia or American Frances Tiafoe for a place in the quarter-finals of the prestigious ATP Masters and WTA hardcourt tournament. bb/js