"Johnny's a great guy, and I think he does get a little bit of a bad rep with that, because Johnny worked very hard for me," Shanahan said. "I really enjoyed coaching him."
Manziel recently voluntarily entered rehab treatment.
"I don't know what he's going through right now, but I think I'm confident Johnny will work it all out," Shanahan said. "And I think he has a chance to have a good future."
Shanahan asked to be let out of his Browns contract with two years remaining. Friction between the front office and coaching staff reportedly led to the departure, although Shanahan declined to confirm this.
He reportedly wasn't happy with Manziel being forced on him as the starter. The Browns also are under investigation for violating rules for texting from the press box to the sideline, an investigation focused on general manager Ray Farmer.
Shanahan did not speak negatively about any situation related to the Browns. He said there were a lot of things he enjoyed about Cleveland, which made it a difficult decision to leave.
"You make some tough decisions, and Cleveland obviously was a tough decision for me," Shanahan said. "Nobody likes to be in the media. I'd rather just hide in the hole and never have to do this, ever. But it's part of the business, and I understand that. But you can't make decisions just based off of that. You've got to make decisions of what you think is best for you, what's best for your family. If you believe it's right, then you live with it. And you live with the consequences and you hope tough decisions end up working out.
"The fact that it's led me to Atlanta and I'm in this situation right now, I couldn't be any happier."
Public Perception Of Gordon And Manziel
Howard Bryant discusses the disturbing inconsistencies in the public's response to recent news about Josh Gordon and Johnny Manziel.