India, Oct. 5 -- Novak Djokovic turned back the clock to produce a sensational come-from-behind win against top seed and fresh-crowned US Open winner Alexander Zverev, winning 4-6, 6-4, 6-4 to reach the China Open semifinals and extend his incredible unbeaten run in the ATP 500 tournament. But the win did not come without tense VAR drama that saw the Serb lose his cool with both the umpire and Zverev.

The incident happened at the start of the match, after Djokovic was broken in the opening game. With the German serving at 30-15 in the opening game, Djokovic won the point, but Zverev immediately walked up to the umpire, complaining that the LED advertising signage had gone dark when he hit the return.

Replays showed that a section of the...