Antonio Brown's crazy antics are cool now while he's one of the best players in the NFL ... but that ish won't fly forever ... so says Brandon Marshall, who tells TMZ Sports he's been in AB's shoes.
Brown's off-season has been filled with turmoil ... from helmet issues to feuds with his old teammates (lookin' at you Big Ben).
Marshall says that's not the biggest deal in the world right now ... but it could be a huge problem in a few years when AB's no longer the hottest receiver in the game.
"When you're a star and you play at the level he plays at, you can get away with things like that."
BM continued ... "When you become a distraction or if you create drama, they'll deal with it when you're balling. But, when you're not, you're the first guy to get shipped out."
Marshall -- who played 13 seasons in the NFL and made 6 Pro Bowls -- understands AB ... 'cause he admittedly had his fair share of drama throughout his career.
"I have an interesting perspective 'cause I've been on both ends, right? I've been a guy that created headlines and distraction at times. And the second half of my career, I was the guy that was trying to be the glue and keep things together."
BTW, the reason Marshall looks so fresh? He was shooting for the season premiere of Inside The NFL -- which airs tonight on Showtime.