Stephen A. Smith says he's devastated over the death of his friend Rasual Butler -- telling TMZ Sports they knew each other for years ... and the NBA player was a really good dude.
"Just incredibly sad," the ESPN star said ... "He's a good guy. We have Philly roots together. I've known him for many years. I love his wife. Love his family."
"The world lost a good brother."
TMZ Sports broke the story ... Butler lost control of his Range Rover in Studio City, CA early Wednesday morning and slammed into a wall -- killing him and his wife, who was a passenger in the car.
Butler was 38.