Andre Agassi called for scheduling changes to reduce player burn-out after pulling out of the season-ending Masters Cup with injury on Monday.
The former world number one became the latest big-name casualty in Shanghai, pulling out with an ankle injury shortly after Spain's Rafael Nadal had withdrawn due to a sore foot.
The loss of Agassi and Nadal was a major blow to the $4.45 million event after Andy Roddick, Lleyton Hewitt and Marat Safin all pulled out with injuries.
"It's just been terrible this year for the number of players who haven't been ready to play here," said Agassi, who pulled out after losing 6-4, 6-2 to Russian Nikolay Davydenko.
"It's probably a sign that things need to change somewhere for guys to feel better about their physical ability to get ready for a tournament this big.
"It's the end of a long year and it's not easy."
The 35-year-old's concerns were echoed by 19-year-old Nadal, who was unable to start his match with Argentina's Gaston Gaudio.
"The calendar is very, very tough," said the French Open champion. "Every player is injured, you know. [Roger] Federer in the last weeks, me...Agassi is injured. Roddick too."
Nadal said he would seek medical advice about possibly cutting back his schedule to avoid burn-out.
"If the doctor says it's safe, I will play the same [number of tournaments] next year," he said. "If he says play less, I will play a little bit less. I want to speak with him."
"MORE VIOLENT"
Agassi acknowledged the game has changed since he beat Sweden's Stefan Edberg to win the season-ending tournament in 1990.
"The physicality of the game [means] it's too difficult for guys to run as hard as they do over and over again," said Agassi, who was appearing in the tournament for a record 13th time.
"The ball's faster, guys are stronger. The movement is much more violent now. This means the potential for more injuries, you know?
"Maybe somewhere, as the athleticism of the game improves, maybe there has to be some adjustments that make it possible for guys to go 100 percent all season."
Agassi added: "Somebody or something has to truly represent the better interest of the sport. It's important for there to be resolve."
The American pointed to Nadal's injury as an example of how much strain the game's punishing schedule is having on players.
"Nadal has raised the bar for how players need to approach this game," said the eight-times Grand Slam winner. "But he's writing cheques you only hope his body can cash.
"He plays very hard every single point. You hope he can stay healthy but it's a lot of wear and tear."
