Serena Williams' former coach at centre of tennis 'cheating' storm

Aussie tennis great Todd Woodbridge has engaged in an ugly war-of-words with renowned coach Patrick Mouratoglou over the ATP's plan to trial off-court coaching.

Coaching during matches is strictly prohibited under tennis rules, although the WTA has previously trialled a system in which coaches were allowed to come down to court level and speak to players.

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It has never been allowed at grand slam level, with Mouratoglou involved in the most infamous case of mid-match coaching in the US Open final in 2018.

Serena Williams was hit with a code violation in the match against Naomi Osaka when chair umpire Carlos Ramos ruled that Mouratoglou was coaching from the stands.

Williams was then handed a point and game penalty after receiving two more code violations in an ugly meltdown that overshadowed Osaka's maiden grand slam triumph.

On Wednesday it was revealed that the men's tour will trial a mid-match coaching system in the second half of the season, with players allowed to get instructions during qualifying and main draw matches in tournaments.

The system will be used at the US Open and ATP Finals - the first time coaching will be allowed at a grand slam.

However the news has been met with a mixed reaction from current and former players, with Woodbridge and Nick Kyrgios expressing their disappointment.

Woodbridge took aim at Mouratoglou on Wednesday night when the Frenchman tweeted his response.

"Congratulations to the ATP for 'legalising' a practice that has been going on at almost every match for decades. No more hypocrisy," Mouratoglou wrote.

Woodbridge interpreted that to mean that Mouratoglou was admitting to illegal coaching and shot back: "This is so disappointing to see that such a high profile coach blatantly admits that he has broken the rules of our sport for so long."

But as Mouratoglou pointed out, he never said he had done it.

"This is a particularly bad one from you Todd. You have been on tour for a long time. Why do you deny the evidence of the coaching happening every day on the courts?" he replied.

"To purposely trying to make me look bad and accusing me? This is disappointing…

"And by the way, learn to read. I never wrote that I was doing what you pretend I wrote."

Kyrgios also tweeted his opposition of the new trial in response to Mouratoglou's comments.

"Completely disagree. Loses one of the only unique traits that no other sport had," the Aussie wrote.

"The player had to figure out things on his own. That was the beauty of it. What happens if a high profile player versus a low ranked player who doesn't have or (cannot) afford a coach?"

Australian Tennis Hall of Fame member David Hall also wrote: “The beauty of tennis was that you had to work your opponent out for yourself. One on one battle.

“This six month off court coaching trial on ATP tour strips it away for no good reason.”

Latest coaching storm for Patrick Mouratoglou

Speaking in 2019, Mouratoglou admitted to gesturing towards Williams during the 2018 US Open final but claimed she didn't see him do it.

Williams vehemently denied she'd received coaching from Mouratoglou and called umpire Ramos a 'liar' for claiming she had.

Mouratoglou is now coaching two-time grand slam champion Simona Halep after splitting with Williams during her recent 12-month absence from tennis.

Another high-profile case occurred at the Australian Open in January when Stefanos Tsitsipas was pinged for receiving instructions from father and coach Apostolos.

During an explosive tirade at the chair umpire, Daniil Medvedev claimed Tsitsipas was being coached by his father, which eventually led to an official being placed at court level underneath where Apostolos was sitting to alert the chair umpire of what he was saying.

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