Rafael Nadal says testing for performance-enhancing drugs in sport should strike a balance between catching the cheats and respecting the athletes.

On Friday at the VTR Open in Chile, Nadal said: "Not everyone has to pay for some sinners."

Nadal said earlier this week that he had passed six blood and urine tests since losing June 28 at Wimbledon. He took seven months off to recover from a left knee injury before returning in Chile.

Nadal says it should be made public who is being tested and how frequently.