SAO PAULO—Rafael Nadal criticized the ATP on Tuesday for not doing enough to protect players' health, saying the increase in hard-court events will lead to long-term injuries that will affect players after they retire.

"The ATP worries too little about the players," said Nadal, who was in Brazil to play his second tournament after a seven-month 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 consider ways to 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 because of the way he's played tennis, it's unlikely he'll be a recreational athlete after his professional career.

"After ending the career it would be nice to be able to play football with friends or tennis," he said. "But with this surface, I don't think it's going to be possible."

The 26-year-old Nadal said hard courts were "too tough" on players' bodies and made it difficult to avoid injuries. Tennis is the only major sport where players have to play on cement, said the greatest clay-court player of the Open era.

"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 about the tour'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 lost in the final of his first comeback tournament in Chile last week, said he wasn't worried about wins and his main focus is 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."

Nadal said he's still feeling pain in his knee, but it's getting better.

"There are days in which it hurts and it limits me physically, but there are days when it's better," he said. "During the bad days it's complicated. But it's positive because a month ago maybe 80 percent of the days were bad, now it's 70 percent of the days and next week or within a month it will probably be 50 percent."

Nadal dismissed changing his style to try to extend his career.

"I'm not that good to be able to reprogram my style, I only have one, it's virtually impossible to change it," he said. "I'm confident that my body will hold up. I'm not sure it will happen next week, or next year, but I'm confident that it will be like before again."

He said he wants to be fully fit to play at the 2016 Rio Olympics, which he acknowledged likely will be his last.

"Playing in 2016 is a long-term goal, but it's very real," he said. "I will be working daily to make sure I can play in 2016 and play well."

Nadal plays doubles on Tuesday and singles on Thursday.

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