Leading tennis coach Patrick Mouratoglou has admitted coaching from the stands has been going on "for decades" as the ATP moves towards legalising the practice.
Men's tennis will trial 'off-court' coaching through the second half of the season, with coaching permitted from designated seats from July.
It means coaching will be permitted at the final grand slam of the year, the US Open in August.
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The ATP has announced verbal coaching will only be permitted when the player is at the same end of the court, while hand signals will be allowed at any time.
Mouratoglou was at the centre of the explosive 2018 US Open women's final between his former pupil Serena Williams and Naomi Osaka, when Williams received a code violation from umpire Carlos Ramos for coaching.
Williams called Ramos "a liar" and "a thief" and said, "I don't cheat ... You owe me an apology."Patrick Mouratoglou with Serena Williams. (Getty)
Responding to the ATP's move to allow coaching, Mouratoglou conceded it had been going on regardless.
"Congratulations to the ATP for "legalising" a practice that has been going on at almost every match for decades. No more hypocrisy," he wrote on Twitter.
That drew a stinging rebuke from Australian tennis legend and Wide World of Sports commentator Todd Woodbridge.
"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," Woodbridge wrote.
Australian star Nick Kyrgios also weighed in, explaining that he was against the change.
"Completely disagree. Loses one of the only unique traits that no other sport had," he 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 afford a coach?"
New York Times tennis writer Christopher Clarey also lamented the change.
"Sad day for tennis in my view," he wrote.
"That the US Open is part of it makes it even sadder. Tennis does not need in-match coaching. It just thinks it does."
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