Green isn't even a Rafalski-level replacement...Mike Green is nowhere near Brian Rafalski in terms of quality. The expectations for Green are out of control. I like the Green signing...a lot, but I know what he is from watching him through the years and last year he was in a perfect spot as a 3rd pairing guy. I will do cartwheels if he can play well with DD on that 2nd pair.
Green was on Washington's 3rd pair in part because of play, yes, but also in part (and I would say at least in equal part) because he was going to be a UFA unlikely to return which is why Washington signed Niskanen to the big deal they did. If they thought Green would/wanted him to stay, Niskanen's never there and he's in the top 3.
Instead the team signs Niskanen to a most likely stupid deal and Orpik to an almost certainly stupid deal and boom... Green's an afterthought the team has no plans on retaining long term or an ability to pay even if they did, so they move on from him in terms of roster responsibility because, well, they're going to have to anyway.
And then he's #2 in goals (t-1st in ES goals) and points among Caps dmen even though he played 72 games at 19:03 per. And he led the dmen in plus/minus.
As a point of comparison, last year all Wings defensemen scored 23 ES goals while Green had 9, alone.
He's going to play 16+ ES, 3+ PP, zero on the PK, and he's going to have a real shot to have the most points of any Wings defensemen since Lidstrom's 62 in 2011.