Rafael Nadal launched an Australian Open broadside at Roger Federer on Sunday, claiming the 16-time Grand Slam title winner should be doing more to support growing complaints over the professional tour.
Nadal has long advocated widespread changes to the playing schedule and even hinted at the US Open last year that strike action could not be ruled out.
The world number two Spaniard believes Federer, who is president of the ATP Player Council, needs to back the top players' complaints.
"It's easy to say I do not say anything, everything is positive and I stay 'a gentleman' while others burn," Nadal told Spanish media here where the first Grand Slam event of the year starts on Monday.
"We each have our opinion and perhaps he likes the circuit. I like it too and it is better than the majority of sports. But that does not mean it can't be better and that things which are bad cannot be changed.
"I speak positively about tennis because I have lived experiences that never in my life could I have dreamed, but to finish your career with pain in all parts of the body is not positive.
"He (Federer) finishes his career like a rose because he has a privileged physique. But neither (Andy) Murray, nor (Novak) Djokovic nor I will finish fresh as a rose."