The ATP was not doing enough to protect players' health and the increase in hard-court events will lead to long-term injuries that will affect players long after they retire, Rafael Nadal said.
"The ATP worries too little about the players," said Nadal, who was in Brazil to play his second tournament after a long layoff from a left-knee injury. "It should care more for them."
The 11-time Grand Slam winner said he doesn't expect major changes anytime soon, but thinks it's time tennis officials start thinking about ways to help improve the players' long-term health.
"For future generations it would be good to see a less aggressive tennis life," he said. "Not only because of what happens during your career, but also because of what happens after your career, about how is your body when your tennis career is over."
Nadal said that because of the way tennis was played, he doesn't "think it will be possible" for him to be a recreational athlete after his professional career.
The 26-year-old Nadal said hard-courts were "too tough" on players' bodies and made it impossible to keep them from getting hurt from time to time. Tennis was the only major sport where players had to play on cement, said the greatest clay-court player of the Open era, and he thinks it's an issue that doctors must get involved with, not only players.
"This is not a subject for the players, it's a matter for doctors," he said.
"The ATP has to start thinking about ways to lengthen the players' careers. I can't imagine football players playing on cement, I can't imagine any other sport involving aggressive movements such as tennis being played on such aggressive surfaces such as ours. We are the only sport in the world making this mistake and it won't change."
Nadal also complained of the ATP's attempt to strictly enforce the 25-second rule between serves, saying it will not benefit the sport.
"People like to see great rallies, long matches, and for that to happen, the 25 seconds are not enough," he said. "If the ATP wants a sport which is faster but doesn't take into consideration a lot of strategy or great rallies, then it's right doing this. I think the players in the locker rooms are not very happy with that rule."
Nadal, who was encouraged in his first comeback tournament in Chile last week in almost winning the title, said he was still not worried about wins and his main focus was to regain rhythm on the court.
"I need time, I need weeks of matches and practice," he said. "I'm not prepared to think about titles yet, I'm thinking day-to-day. After so many months without playing it's hard to think about titles."
He was to play his first-round doubles on Tuesday (local time), and his first singles on Thursday.