Based on Dennis Lehane's novel, the film is about two private detectives searching Boston's seedy underworld for a 4-year-old girl who has vanished.
"I feel like ('Gone Baby Gone') is the linchpin for my life. My career. I have a lot riding on it," Affleck told Details magazine. "I want (the film) to work. Badly. I mean, a shitty movie comes out on 2,800 screens? I’ve been there and it’s embarrassing."
The film marks Affleck's directorial debut.
"That’s why there’s something really great about directing -- about having authorship over something. If you don’t like this movie, I’m the guy to see. I’m the guy to criticize. I take some measure of comfort in that. It’s fair, at least," he said.
The actor-turned-auteur also called his brother "the obvious choice by far" for the film's lead role.
"I think he’s a really good actor, but he also had the benefit of people not being as aware of him. Other actors, you have this expectation of what they’ll do. But Casey? He could surprise you," Affleck said.