Brad Paisley is a MASSIVE Cleveland Browns fan -- and you can tell he's genuinely sad about the incident with Myles Garrett ... explaining why the helmet-swing was heartbreaking to watch.
"Wish he hadn't done what he did," the country music superstar tells TMZ Sports ... "It's crazy. He shouldn't have done that."
Paisley has spent a lot of time around the Browns (remember his "Hard Knocks" cameo at training camp?) ... and says he's heard Garrett is a good dude, which makes it harder to understand why he went so crazy against the Pittsburgh Steelers last week.
"I'd love to know what he's thinking. I'm sure he's remorseful."
Even if Garrett can bounce back from the scandal, Paisley says he'll NEVER win back Steelers fans ... saying, "Pittsburgh will never forgive him, I'm sure."
As for the punishment, Paisley says he'll support whatever suspension the NFL eventually dishes out -- "He needs to serve that time, whatever they decide that is."
The league has already suspended Garrett for the rest of the year, but he's appealing this week and the punishment COULD change (maybe).
So, why is Paisley -- who's from West Virginia -- a Browns fan? It all stems back to Brian Sipe ... (betcha didn't think you'd see that name today!)