"Four weeks - four different balls. When are tournaments going to listen to players??"
Three-time Grand Slam champion Stan Wawrinka was speaking for many professionals in his social media post of late October.
Nick Kyrgios sympathises, with the Australian speculating that Novak Djokovic's current wrist and forearm issue might be down to changes in the balls.
"Changes of balls every week finally got to Novak's wrist," posted Kyrgios, the 2022 Wimbledon runner-up, after the world number one had treatment on court in Perth this week.
"The ATP really need to do something about the problem.