Is having three catchers really that bad? With two catchers, the second rarley gets into the game unless it is an emergency. With three, the third won't likely see action, but the manager has the option of using one to pinch hit from the left or one from the right. There is the option of pinch running for one if needed because there is still that safety valve provided by the third catcher.
Really, Valentin is a versitile component that is available to catch, play first, or pinch hit. He removes that "last off the bench" handicap that is always affixed to the second catcher. I think it is more like having 2 and 1/3 catchers and it gives the manager more versitility than if he just had two catchers.