There's no rationalization. Hamels sucks. Yeah, they gave up nothing, but he could, and probably will, cost them wins. Nothing significant, but he's been absolutely awful the last month, and wasn't great before that. Could be a change of scenery will be good for him. I personally doubt it. I'd say the same thing if the Brewers acquired him, and will say the same thing if the Brewers acquire Matt Harvey, who also sucks.