Myles Garrett is a good person who made one HUGE mistake ... so says ex-Browns asst. coach Bob Wylie who tells TMZ Sports the helmet-swinging maniac is "not the real Myles Garrett I know."
You probably remember Wylie from "Hard Knocks" -- he worked alongside Garrett as an assistant coach from 2017-18 (remember the belly-shaking "set, HUT!").
Wylie says he was disappointed to see the DE weaponize a helmet against Mason Rudolph during Thursday night's game against the Steelers ... but hopes it doesn't permanently ruin MG's reputation.
"He's not a bad person, he's a real good kid and he plays a violent sport," Wylie says.
"You play right on the edge and he plays right on the edge of the sport. And, he went over the edge."
The former offensive line coach says Garrett is a model teammate who went out of his way to help Wylie's guys ... and he NEVER saw an outburst like that before.
"All the times I spent with him on the practice field and in meetings, I never saw that Myles. I saw his effort, I saw his ability to compete, I saw his study habits ... but I never saw that."
The NFL has suspended Garrett for the rest of the 2019 season -- though he plans to appeal. Garrett has since apologized to Rudolph and his teammates.