Nick Kyrgios has lamented the ATP Tour trialling off-court coaching, warning tennis will lose one of the "unique traits that no other sport had".
The ATP announced on Tuesday that off-court coaching will be tested in the second half of the season, with coaching permitted by a designated person in qualifying and main draw matches.
Verbal coaching will be permitted when players are at the same side of the court as their coach, with non-verbal instructions – for example hand signals – allowed at any time.
Patrick Mouratoglou coached former world number one Serena Williams and now works with Simona Halep, and was quick to welcome the introduction.
Mouratoglou suggested the coaching methods have been used at "almost every match for decades".
While Mouratoglou was a vocal supporter of the ATP decision, Kyrgios – who pulled out of the Mallorca Championships with injury – hit back and slammed the proposed changes.
"Completely disagree. Loses one of the only unique traits that no other sport had," Kyrgios responded to Mouratoglou's post on Twitter.
"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?"
The trial commences on July 11 and will be evaluated at the end of the 2022 season, to assess the potential inclusion of off-court coaching in subsequent seasons.