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 heart-breaking 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.