Well, from Joe Torre himself:
Theriot’s got a little more punch. Last night, in fact, he hit one to the wall in right center. And Carroll handles the eighth spot. I’m sure Theriot would too, but right now, I think we have more flexibility with Theriot in the [second spot].
We might change that at some point, but I’m happy with Theriot right now.
Theriot actually has had a better slugging and ISOP this year than Carroll, but only because Carroll literally hits nothing but singles. While Carroll’s enjoying an awesome year at the plate, especially in patience, Theriot has three-year slash stats trending downward. So that’s something to not like.
Edit: This isn’t necessarily about Carroll or Theriot or anyone on the Dodgers for that matter, but I do get the feeling some players tie their ego into the batting order and so seeing some guy at the top of the order when he doesn’t deserve to be there could be because of that. Should a manager make those decisions to goad the player’s ego? I don’t know, I’ve never played professional baseball and that is one of those “clubhouse” things. But it’s really the manager’s prerogative and batting order doesn’t matter so much, so take that as you will.