I read that McShane repaced Evan for the last 13 mins or so anyway.
He's still work-in-progress as we all know. Andy O'Brien on the other hand is playing very well, is 28 (I think) a really good age for a CB and is the type of CB whose style would most complement Dunne's in my opinion.
Finnan-Dunne-O'Brien-O'Shea is my preferred back 4 if everyone is fit. O'Shea is a worry but it's experienced without being old and would be a good foundation for the rest of the team.