Thanasi Kokkinakis made a winning return to Miami on Thursday, earning a first-round win at the venue where he stunned Roger Federer three years ago.
The injury-prone Aussie whose career has moved in fits and starts, pulled up healthy and showed what he can do when fit, defeating Shintaro Mocuiziki of Japan 6-3, 6-3.
Kokkinakis, with a 243rd ranking, broke five times to earn his second win of the season from four played. he last competed in the Australian Open second round losing in five sets to Stefanos Tsitsipas after coming back from another injury break of nearly a year and a half.
Mochizuki, aged 17, won 2019 junior Wimbledon and was playing in a Masters 1000 field for the first time ranked 630.
Kokkinakis fought back from 0-40 down in the opening game to get one his way against his teenaged opponent; he next faces Hungarian Marton Fucsovics.