"He's erratic," Bradshaw told us in NYC ... "His behavior makes me nervous. I don't know what's wrong with him. It makes no sense."
AB added another chapter to one of the most bizarre NFL stories ever on Thursday ... quitting the league in a profanity-laced social media rant, before eventually backtracking.
Bradshaw agrees the 31-year-old WR is crazy talented, but the off-the-field issues could be too big of a hurdle for him to overcome.
"Ya gotta deal with a lot of stuff. Are you willing to do that?"
Bradshaw says if he were running an NFL team, "I'd have to sit him down and I gotta make sure he's okay."
Brown has already been cut by TWO teams this season -- the Raiders and the Patriots -- and he cussed out the NFL on Thursday, saying the league treats black players unfairly.
The Seattle Seahawks reportedly looked into signing Brown recently but opted to sign Josh Gordon instead ... ultimately deciding Brown was not worth the trouble.
Brown is also being investigated by the NFL over allegations he raped his former trainer at his home in 2018. AB has denied the allegations and said the accuser's lawsuit is nothing more than a cash grab.
And, don't forget ... while Brown was on the Pats, he sent menacing text messages to a woman who accused him of sexual misconduct. The NFL is investigating that incident as well.