"There's a scapegoat in every situation, and who's the scapegoat? Robert Griffin," McNabb told Fox Sports.
"This is something that I've seen, obviously, when I was in Washington and I've been seeing it since I left, at what point as a head coach will you say, 'I need to get the guys prepared.
"It's my fault. We didn't play well, I'll make sure that we're ready tomorrow. This is something that's been a problem, even since when I was there, when things go wrong."
The Redskins face the New York Giants on Sunday.