Rafael Nadal has criticized Roger Federer for letting other players "burn themselves" by complaining about tour conditions while maintaining his good reputation by rarely making negative comments about tennis.
The two have always been respectful rivals, but the ongoing debate about the overcrowded tennis calendar has exposed a difference of opinion on the eve of the Australian Open.
After telling a pre-tournament news conference Sunday he had no intention of being the frontman for the players' grievances because it has reflected badly on him in the past, Nadal was then critical of 16-time Grand Slam winner Federer in a Spanish-language interview.
Responding to the suggestion that Federer disliked players complaining openly about problems on the tour because it tarnished the image of tennis, Nadal said he took another view.
"No, I totally disagree," he said in comments translated from Spanish. "For him it's good to say nothing. Everything positive. 'It's all well and good for me, I look like a gentleman,' and the rest can burn themselves.
"Everyone is entitled to have their own opinions."
Nadal and No. 4-ranked Andy Murray are among the players who have been outspoken in recent months on issues including an overcrowded calendar and the scheduling of Davis Cup matches. Some players have talked of strike action as recently as Saturday's player meeting in Melbourne; Nadal has said players may have to resort to "strong action" if there isn't an "evolution" in the calendar.
Federer and Nadal, who has 10 Grand Slam titles, dominated men's tennis for the seven years before Novak Djokovic won three of the four majors in 2011 and passed them both for the No. 1 ranking.
They're both key ambassadors for the tour, helping with promotional work and appearances at tournaments around the globe.
Nadal thinks that when players highlight problems on the tour, the intention is to make it better, not run it down.
"He (Federer) likes the circuit. I like the circuit," Nadal said. "It's much better than many other sports but that doesn't mean that it couldn't be better. It doesn't mean there are some things about the tour that could change. The tour is fine, but there are some things that are bad. That's all we're saying.
"And the vast majority of players have this same opinion. He's got a different opinion ... if the vast majority have one opinion, and a small minority think differently, maybe it's them who are wrong."
For the first time since the 2005 French Open, Federer and Nadal are on the same side of the draw at a major, which means only one of them can reach the final on Jan. 29.
They both start Monday. Third-seeded Federer, a four-time Australian Open winner, is on Rod Laver Arena in a night match against Russian qualifier Alexander Kudryavtsev.
No. 2-ranked Nadal has the last match on Hisense Arena - the second show court at Melbourne Park - against Russian Alex Kuznetsov.
Defending champion Djokovic doesn't start until Tuesday. Women's champion Kim Clijsters' is the third match on Rod Laver Arena on Monday against Maria Joao Koehler of Portugal.
Li Na, who lost the Australian final last year but rebounded to win the French Open to become China's first Grand Slam singles champion, has a first-round match against Ksenia Pervak of Kazakhstan and No. 1-seeded Caroline Wozniacki, still searching for a maiden major title, faces Australia's Anastasia Rodionova.
While the last eight women's Grand Slam titles have been won by six women and the draw in Melbourne is wide open, the men's tournament is widely tipped to go to one of the top four.
Since winning the Australian title in 2009, Nadal has lost in the quarterfinals the last two years, both times hampered by injuries. He has had a sore left shoulder since late last season and is planning on taking a rest after the Australian Open.
Many players are calling for more rest due to the increasing pace of the game and the physical strength and endurance required to compete at the highest level.
Federer, now 30, quickly earned a reputation as a tennis statesman when he started accumulating major titles with such a graceful and seemingly effortless style that critics wondered if anyone could challenge him on any surface except clay.
Then Nadal started winning majors away from Roland Garros, with a high-energy game well suited to his muscular physique. But he thinks that has come at a cost.
"I love the game and there's a lot of things I'm grateful for. The game has allowed me to lead a fantastic lifestyle," he said. "But to finish your career with pain all over your body, is that a positive? No.
"Maybe (Federer) has got a super body and he'll finish his career like a rose. Neither myself, nor Murray, nor Djokovic are going to finish our careers like a rose.
"Tennis is an important part of my life, but it's a tough sport. We're not like him where it's effortless to play. All of us, it's a battle."
Nadal said his knees, hips, back and ankles were prone to soreness because "every year the ball flies quicker, there's more intensity. The surfaces are hard."
The ATP, which runs men's tennis, declined comment on the player meeting in Melbourne on Saturday where concerns were raised again. Other players, including former top-ranked Lleyton Hewitt, didn't want to discuss the meeting because they were concentrating on the Grand Slam tournament.
While not wanting to represent the group, Nadal did say he was confident small changes could be made to the calendar without any drastic effects on the sport.