Aldon Smith's alcohol problem got so bad, he was drinking every single day ... and people close to the embattled NFL star are concerned he'll drink himself to death if he continues down this road.
"I'm worried for him. I'm worried for his safety," one source close to Smith tells TMZ Sports.
"He's an alcoholic. It's not about football anymore. We're hoping this is rock bottom for him."
We broke the story ... Aldon checked into a rehab facility on Sunday after a domestic violence incident with his fiancee ... the latest in a string of alcohol-related incidents that includes two DUI arrests.
Smith's fiancee previously told us Aldon contacted her father after the domestic violence incident (he's a doctor) and asked for help. They felt the best move was to go to rehab.
Smith's former Raiders head coach Jack Del Rio believes Aldon's NFL suspension stemming from a DUI hasn't helped -- the isolation from his team has only made his situation worse.
"Never liked 'league rules' that eliminate the ability of teams to offer Aldon and others in his situation the structure they so desperately need."
Raiders lineman Donald Penn made the same points back in March when he told us Smith would benefit from being around teammates who care about him.
Hall of Famer Tim Brown had also suggested the team hold intervention-type meetings with the struggling star after another drunken run in with police.