Roddick (left) and Nadal are in action in Shanghai
Rafael Nadal and Andy Roddick have questioned the length of the ATP season and suggested that tennis players need a proper off-season.
World number two Nadal and world number six Roddick are currently in China for the Shanghai Masters.
"It's impossible to play 1 January and finish 5 December," said Nadal.
American Roddick said: "It's ridiculous that you have a professional sport that doesn't have a legitimate off-season to rest, get healthy, and then train."
The 27-year-old added: "I just feel sooner or later that common sense has to prevail."
I don't see any other sporting leagues or federations following our lead as far as not being individually represented
The top players on the men's tour are required to play in eight of the nine Master Series events, with Monte Carlo the exception.
And the top eight players of the year are required to play an extra week by qualifying for next month's season-ending tournament in London.
Roddick said merging the players' union and tournament operation under the ATP umbrella, which took place in 1990, has not benefited players as expected.
"I certainly don't see any other sporting leagues or federations following our lead as far as not being individually represented," Roddick said.
Nadal, who did not defend his Wimbledon title this year because of a knee injury, added: "It's impossible... being all the time 100% without problems."
Both world number one Roger Federer (fatigue) and Britain's world number three Andy Murray (wrist injury) are skipping the Shanghai tournament.
Thirteenth seed Radek Stepanek beat former world number one Juan Carlos Ferrero 6-3 6-0 in the first round on Monday, while 16th seed David Ferrer beat Richard Gasquet 6-4 6-3.
Fourteenth seed Tommy Robredo defeated French qualifier Michel Llodra 6-1 6-4, while 10th seed Fernando Gonzalez was handed his place in the next round when Germany's Mischa Zverev retired hurt with a wrist injury in the third set.
James Blake was made to work hard by Ivo Karlovic before eventually overcoming the Croatian 3-6 7-6 (7-4) 6-3 to set up a second-round clash with Nadal.
Marat Safin, who is set to retire at the end of the season, was a convincing 6-4 6-4 victor over Chinese wildcard Gong Mao-Xin.