Dennis Rodman says Antonio Brown is a case study on self-sabotage ... telling TMZ Sports the guy basically ran a clinic, "The school of how to ruin your career 101."
Rodman was leaving the Javits Center in L.A. on Sunday with his good friend, Dr. Drew -- when the topic turned to AB's social meltdown over the weekend.
As we previously reported, the troubled WR let his Twitter fingers loose ... saying he's done playing in the NFL while taking shots at his former boss, New England Patriots owner Robert Kraft.
Even Rodman was shocked by AB's antics ... and that's saying A LOT. He tried to break it down to us.
"Antonio Brown ... he wasn't focusing enough on his career."
Rodman says Brown tried to be clever but "outsmarted himself" and now HAS to quit the NFL because he basically "has no choice right now."
That said, you can tell Rodman and Dr. Drew hope Brown can get his life back on track -- with Rodman noting, "We all make mistakes."