World No 6 Taylor Fritz said the International Tennis Federation's (ITF) decision to allow off-court coaching from 2025 would ruin the one v one strategic and mental elements of the game.
The ITF announced on Monday that off-court coaching will be allowed from January 1 following a decision made at the governing body's annual general meeting this month.
It said the change would make tennis "fairer and, potentially, more entertaining".
Off-court coaching had already been implemented on a trial basis in all four Grand Slams as well as the ATP and WTA tours since 2023.
US Open finalist Fritz had previously been critical of off-court coaching and expressed his displeasure with the rule change in a post on X on Monday, writing: "Can we stop ruining the 1v1 mental/strategic aspect of the sport PLEASE."
Former world number 10 Denis Shapovalov said the decision to allow off-court coaching was "sad to see" as a fan of the sport.
"Tennis is special because you are out there alone. Why are you trying to change the beauty of this game," the Canadian posted on X.
ITF senior Executive Director Stuart Miller said the decision had been made after consulting with key stakeholders including players, coaches and umpires.
"Players felt it was a positive development and makes tournaments more interesting for them. Coaches have said it helps player development and helps to improve the standing of their profession," Miller added.
"Chair umpires have said it improves their ability to focus on monitoring the game and making the right decisions, rather than whether or not a coach is coaching against the rules."