‘Most stupid rule’: Novak Djokovic loses his cool, clashes with umpire and Alexander Zverev as VAR drama erupts in tense China Open win

The quarterfinal contest was briefly interrupted by a moment of controversy that left Novak Djokovic angry

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.

Serbia's Novak Djokovic (R) and Germany's Alexander Zverev argue with the referee during their men's singles quarter-final at the China Open (AFP)

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 signage had switched off, though not as Zverev was hitting the forehand. The chair umpire ordered the point to be replayed, prompting a frustrated exchange from Djokovic.

Djokovic said: "I served, he played another shot, is that OK? Like that, it changed there. He played after the serve. It doesn't make any sense."

As Djokovic argued with the umpire, Zverev stuck his nose in, saying: "I didn't know about the challenge, that's why I came to him and asked," to which an increasingly angry Serb said: “But then you [should] stop after the serve? This must be the most stupid change of rules I've ever heard in my life. It makes no sense. We could play a 30-shot rally and he could lose the point and say: 'OK, I'm going to challenge now'.”

"This is absolutely fascinating. I have never, ever seen this. It would be a first if they replayed the point.

"It changed before the point. I guess there they should have stopped the point... I think Djokovic is right. I've never seen anything so ridiculous in my life. I cannot believe they have made this decision."

Djokovic did not get the break back and went on to lose the opening set, but he broke at 5-4 in the second to level the match, shifting the momentum in his favour after a tightly contested battle.

With little separating the pair in the third, the Serbian struck again at 5-4 on Zverev's serve, securing the decisive break to seal victory in two hours and 35 minutes.

"I was trying to be aggressive and come to the net, and change up the pace, not giving the same pattern," Djokovic said.

"I am just glad that I held my nerves, played good shots at important moments, 5-4 in the second and third."