The "Friends" actor played pickleball religiously at Riviera Country Club near his L.A. area home -- and he even had a personal coach, Matt Manasse.

Manasse told People magazine ... Perry used the game as a tool to keep him away from drugs and on the straight and narrow.

"He thought it was something that could help in his recovery and he was doing an awesome job," Manasse said.

Manasse noted Perry was so passionate about the game he would play five times a week and talk incessantly about it.

"[Perry] got so much better, always made everyone laugh," Manasse said, adding, "He was competitive, not in a bad way at all. He loved it. When he hit an unbelievable shot, he would tell you about it for days."

Manasse also described Perry as a caring person who was always trying to help others, especially recovering addicts by introducing them to pickleball at Riviera.

TMZ broke the story ... Perry, 54, apparently drowned in his jacuzzi Saturday after playing 2 hours of pickleball at the country club. We're told he was in good spirits during the game.

Later that afternoon, his assistant returned to his house after running errands and discovered Perry was unresponsive. The assistant called 911, Perry's mother and one of his siblings, as well as another person.

Law enforcement tells us ... authorities discovered anti-depressants, anti-anxiety drugs and a COPD drug inside Perry's house. COPD refers to Chronic Obstructive Pulmonary Disease, which is often used to treat emphysema or chronic bronchitis. Perry smoked cigarettes during his life.