I'm not sure how much the Cubs are really going to be able to squeeze out of us for Luis Valbuena. If some other team with a hole at third or second calls up and Chicago tries to instigate a bidding war, sure, you have to avoid that. Valbuena isn't worth that.
But I'm a big believer in the idea that championship teams tend to have role players who are slightly over-qualified for their positions. I think about the 2001 Diamondbacks team that used Erubiel Durazo, Greg Colbrunn and David Delucci as pinch hitters when all could have easily handled platoon arrangements at least. Valbuena gives us some pop and patience off the bench, and insurance at a couple positions.
We won't platoon him with Johnson, but he lets us sit CJ down against really tough righties from time-to-time, and he's a good security blanket should La Stella hit the rookie wall.