George Clooney is speaking out publicly about the death of Matthew Perry ... saying the actor wasn't happy on the set of his hit sitcom, "Friends."
Clooney sat for an interview published Tuesday in Deadline to promote his new film, "The Boys In the Boat," -- and he opened up about his relationship with Perry dating back to the '90s when they first met and played paddle ball together.
As you know ... Perry died of "the acute effects of ketamine," a drug used to treat depression and is sometimes taken recreationally. The L.A. Coroner found several contributing factors: drowning, coronary artery disease, and buprenorphine effects. Buprenorphine is used to ween addicts off opioids.
In October, Perry was discovered unresponsive in his hot tub after his personal assistant returned to his L.A. area home after running errands. Perry was declared dead after first responders tried unsuccessfully to revive him.