World number two Rafael Nadal criticised the ATP on Thursday for promoting a court surface he said was the toughest on the bodies of the players.
The Wimbledon and French Open champion claimed his fifth successive title and seventh of the year when he won the Toronto hardcourt tournament last week.
But the Spaniard said the sport's governing body was not paying enough attention to the effect of hard courts on injuries.
"The top management of the ATP are ... always thinking about playing more and more tournaments on this kind of surface," Nadal told a news conference.
"It's not good because if you look at the locker room and the trainers' room, everybody has problems. It's the hardest surface on the body for sure.
"Not everyone has the same (injury) but I've seen a lot of players with problems in the knees and feet. Everybody is taped up."
Five of the nine Masters Series are hardcourt tournaments and so are two of the four grand slams -- although grand slams are not part of the ATP Tour.
Of the 52 tournaments below Masters Series status, 26 are on hard courts (eight indoors) but players usually feel they cannot afford to miss them as they build up to playing in the bigger events on the surface.