That's ex-NFL star Martellus Bennett -- who played 10 years in the league -- explaining how football affected his mental health ... saying the game and the culture take a real, dangerous toll on players and it's concerning.

"Football is interesting. Psychologically it’s some really dangerous s**t. To really play the game of football you have to have some f**ked up wiring in your head."

Bennett explained, "It’s chaotic. It takes years and years of brainwashing to go along with a lot of the s**t. Lol. It starts at pee wee. That’s why you gotta watch who is coaching your kids and what they’re teaching them beyond the game."

The 33-year-old Super Bowl champ says from a young age, football players are groomed to "care a little less about humans."

"If you’re the backup and the man in front of you go down. You kinda get excited but feel bad at the same time. Hahahah. S**t's crazy."

Bennett also takes aim at football coaches -- saying most are not good men. Unclear if he's referring to any specific college or NFL coaches in particular.

"Most of them are egotistical small d**k heroes. They love the spotlight just as much as the players. Lol. And, they be dumb too."

Bennett also had some news for NFL fans about their favorite players -- saying most of them are bad people off the field.

"Most of your favorite players aren’t good people. Hahaha. Like for real for real."

"There are some good dudes tho. [ex-NFL quarterback] Jon Kitna is probably one of the best people I’ve ever met. He’s up there with Tom Hanks."

In a long series of posts on social media, Bennett also explains why so many NFL players have such a hard time "integrating back into everyday society" when their playing days are over.

"The constant reminder of who you used to be by fans and trophies and highlights and family as you’re trying to transition into the new you really slows down the process."

Despite his blunt honesty, Marty says he's not "s**tting on football" -- "I just provide a different perspective on the experience."