Tennis players risk injury because of the constant change of ball designs at tournaments, according to world number twoRafael Nadal.
Nadal echoed Shanghai Masters defending champion Andy Murray in complaining that commercial pressure from tournament sponsors had resulted in three ball changes over the last three events in Asia.
"You play in Bangkok with one ball, in Tokyo with another ball, here with another ball. That's too much in my opinion. (It) is dangerous and can cause injuries," said the 25-year-old Spaniard after his second-round win in Shanghai.
"Something must change because is too dangerous for the shoulders. You cannot change the ball every week."
Nadal said he would prefer to receive less prize money in return for less pressure from sponsors to use different balls.
"I am very happy to win less money and have my health," he said.
"If we compare the Tokyo ball with this one (in Shanghai), it was much bigger, slower. The ball is completely different. This ball is very fast, it goes small and doesn't stay on the racquet. It flies a lot and is tough," said Nadal after beating compatriot Guillermo Garcia-Lopez 6-3 6-2 to reach the third round.
"It is not necessary to have a standard ball for the whole season," said the Spaniard.
"For example, when you start the clay-court season, you have the same ball for that period; when you have the American hard court season, you have the same ball. So that's positive.
"But what cannot happen is to have one ball in Rome, one ball in Madrid, one ball in Barcelona... That doesn't work."
Murray, on Tuesday, also called for more consistency in the balls, saying: "If you asked a golfer to change balls every single week, they'd be hitting balls 20 yards too far and hitting shots all over the place."
Nadal said other players were equally unhappy.
"A lot of players believe this. That's something that, in my opinion, can change," he said.