Both players, who are in China for the Shanghai Masters, reiterated criticism of the sport's punishing schedule.
"It's impossible to play 1st of January and finish 5th of December," said the 23-year-old Nadal, who did not defend his title at Wimbledon because of a knee injury. "It's impossible to be here playing like what I did the last five years, playing a lot of matches and being all the time 100 percent without problems."
Roddick, a veteran at 27, said players need a longer offseason to recover, and noted that both Roger Federer (fatigue) and Andy Murray (wrist injury) are skipping the Shanghai tournament.
"It's ridiculous to think that you have a professional sport that doesn't have a legitimate offseason to rest, get healthy, and then train," Roddick said. "I just feel sooner or later that common sense has to prevail."
The top players on the men's tour are required to play at eight of the nine Master Series events - with Monte Carlo being the exception. And the top eight players of the year also have an extra week by qualifying for next month's season-ending tournament in London.
Roddick said that merging the player's union and tournament operation under the ATP umbrella, which was considered a cutting-edge concept that would benefit the players when instituted in 1990, hasn't turned out to be overwhelmingly positive.
"I certainly don't see any other sporting leagues or federations following our lead as far as not being individually represented," Roddick said. "I don't know that it's up to the players to be making business decisions about the schedule. At a certain point, I wish our input would be.
"It's got to be someone's job to figure that out, right?"