In my mind the same question exists, to varying degrees for each of Outman, Clemens, and Wallner
Who are you going to replace them with, where you're happy with the roll that new player is going to take on, or what it does to the rest of the players playing time?
a) Outman. He's barely playing. There's nobody at AAA that I want barely playing. Especially with the current emergence of Martin, who's soaking up what little playing time Outman was getting.
b) Clemens. When he plays, it's 1B. There's nobody worth calling up from AAA that can play 1B, so you're going to get a heavy mix of Caratini and Bell over there. Not a great option (not that Clemens playing 1B is some great option).
c) Wallner. Probably the easiest 1-for-1 swap since he's both getting a ton of playing time and is a lefty outfielder which we have in spades at AAA. The problem here is that he's the one I'm least interested in giving up on.