Shot fired: Russian tennis ace Kafelnikov warns Djokovic risked KNOCKING OUT judge as he compared drama to 'EXTREMELY RUDE' Serena

Ex-world number one Evgeny Kafelnikov has said that successor Novak Djokovic was treated "absolutely fairly" when he was disqualified from the US Open on Sunday, echoing his thoughts on Serena Williams' shame in New York in 2009.

Two-time Grand Slam winner Kafelnikov claimed there was no discussion to be had about disgraced Djokovic's disqualification from the tournament, where he defaulted in the first set against Pablo Carreno Busta after hitting a ball at a line judge.

Fans of the controversial Serb have debated whether the favorite meant to hit a female line judge in the throat as he frustratedly fired a ball at the back of the court, but Kafelnikov has said that Djokovic could not argue against his punishment and "understands it perfectly."

"I don’t think he thought about the repercussions," Kafelnikov, the 1997 US Open champion, told Soviet Sport.

"He hit [the ball] against the wall so that it would be loud.

"A half-power shot from Djokovic could knock an unsuspecting person out cold – especially a woman.

"I don’t know what was happening with him earlier on in the match, but on every replay it is clear that he intentionally struck the ball towards the officials. And not just like returning the ball back to a ball boys...[it was] with a half-strength shot. They defaulted him absolutely fairly.

"It’s possible he wanted the shot to make a noise off the wall, at which the official would notice and understand his frustration."

After apologizing and checking on the judge's welfare, Djokovic remonstrated with officials at the net before making his way off court as he digested his disqualification.

He has since asked his millions of fans to be "especially supportive and caring" to her, with reports claiming that she has been sent death threats.

Kafelnikov said that emotions had got the better of Djokovic, just as they did for Williams when she famously lost her temper in her semifinal against Kim Clijsters, warning a judge: "I swear to God, I'll f*cking take the ball and shove it down your f*cking throat."

"There was no contact then, just a verbal exchange," the 46-year-old pointed out.

"It was extremely rude from Serena’s side and the decision was absolutely understandable."

Williams was fined $10,500 for her tirade, and Djokovic will pay $10,000 for unsportsmanlike conduct – half the maximum penalty for the offense at a Grand Slam.

Djokovic has also forfeited $250,000 in prize money and squandered the chance to win his 18th Grand Slam in the absence of main rivals Roger Federer and Rafael Nadal.