Novak Djokovic blasted the absence of video technology as "embarrassing" on Sunday as the Olympic champion and 24-time Grand Slam title winner weighed in on an umpiring row at the Cincinnati Masters.

Jack Draper defeated Felix Auger-Aliassime at the US Open warm-up event on Friday despite a suspicion the ball hit the Briton's racquet and then the floor before it popped over the net to secure the match-winning point.

Despite the Canadian's protests, the point was ruled legitimate by the chair umpire and Draper was declared the winner.

"It's embarrassing that we don't have video replay of these kind of situations on the court," Djokovic, who is not playing at the tournament, wrote on social media.

"What's even more ridiculous is that we don't have the rule in place that would allow chair umpires to change the original call based on the video review that happens off the court!

"Everyone who watches TV sees what happened on the replay, yet the players on the court are kept in the 'dark' not knowing what's the outcome."

The Serb star added: "We have Hawkeye for line calls, we live in the technologically advanced 21st century! Please respective Tours, make sure this nonsense never happens again!"

The US Open, the last Grand Slam event of the season, uses video replay but it is widely absent from tour events.

American star Coco Gauff also demanded the introduction of video replays after being dumped out of the Olympic Games at Roland Garros in Paris last month

US Open champion and world number two Gauff became embroiled in a tearful, bitter dispute with the chair umpire over a line call during her loss to Donna Vekic.

She had also argued with the umpire during her semi-final defeat to Iga Swiatek at the French Open on the same courts in June.

Again, the dispute centred on a line call.

"I'm getting cheated in this game. You guys are not fair to me," Gauff told the chair umpire at the Olympics.

"I feel like in tennis, we should have a VR (video review) system because these points are big deals. And, yeah, usually afterwards, they apologise, so it's kind of frustrating when the sorry doesn't help you once the match is over," she said.