Vidic wouldn't really offer us anything.
Tbh unless we're getting Thiago Silva for free off of PSG to entice us to sell Pogba, we really shouldn't be looking at first team CBs until Barzagli (God forbid) starts declining sharply.
So, basically. It's not going to happen so why waste a penny on it
I imagine he'd be an upgrade for Inter, definitely an upgrade for Milan. So, meh. Let him go.