The deal when made official is expected to be worth up to £700,000 after appearance bonuses, with McClain saying that the move would be "perfect" for him.
"It's a move that can't go wrong and I'm looking forward to playing in Baltimore as the Ravens run the same or very similar defense as I was a part of at the University of Alabama," he told Madison Weekly News.
"Ray Lewis retired after winning the Super Bowl and I look to fill his slot. No one can fill his shoes, but I can fill his slot. I just want to fill out the shoes of Rolando McClain. This is a perfect fit for me personally."
McClain made 62 combined tackles for the Raiders last season.