South Korea's Hyeon Chung got the better of third seed Denis Shapovalov in the opening round of the Next Gen ATP Finals in Milan, Italy.
In a tournament which is trailing a shot-clock, first-to-four sets, and no doubles tramlines on court, Chung prevailed 1-4, 4-3 (5), 4-3 (4), 4-1 in just over an hour and a half.
It wasn't the only surprise result on the first day of the tournament as Daniil Medvedev beat second seed Karen Khachanov 2-4, 4-3 (6), 4-3 (3), 4-2.
Elsewhere Borna Coric defeated American Jared Donaldson in straight sets.