Don't consider either of them a game manager, but just saying if McCarron had been our QB last year he probably wouldn't have had much better numbers than are QBs. Clausen is a similar case to McCarron though: Great O-Line, special running backs, and dink-and-dump to explosive receivers w/ an occasional well-thrown deep ball. Casey didn't do much in the pros and, I might be wrong, McCarron probably won't either.
Edit: So now that I think about it, I might consider both of them excellent 'game managers'. If that makes sense LOL...