India, Oct. 6 -- Daniil Medvedev's China Open campaign ended in a way rarely seen in tennis. Ironically, it came against Novak Djokovic, who had suffered a similar fate six years earlier at the US Open. With the Serb serving for a spot in the final and leading 7-5, 5-3, the Russian, in apparent frustration, struck the rebounding ball into the stands, where it hit a spectator sitting directly behind him. He waved his hand in apology, but there was little argument he could make after he was defaulted following a discussion with the chair umpire and a tournament official. Djokovic went through to the final.

The ATP Rulebook's Code of Conduct (Section 8.04.L.4.a, the "Ball Abuse" rule) bars players from hitting the ball "violently, dangerous...