With Punto being activated from the DL, it was going to be either Casilla or Tolbert sent back down to AAA Rochester. Tolbert has been doing the things that Casilla hasn't, which is why Casilla is being sent down.
Casilla doesn't understand why he's being sent down, but that just doesn't make sense. He hasn't been playing the small ball the Twins need him to, and he's been making dumb mistakes. He was tearing the cover off the ball down in AAA before he was called up, so maybe he just needs some more time down there again to clear his head and do what it takes to be productive at the big league level.
Twins send Casilla down