This was almost definitely part of the original deal, no? Baltimore willing to trade him as a rental with a handshake they would get him back for next year. Sure the Cubs could have reneged, but not without the word getting out. I don't think we as common fans realize how often these kinds of "you owe me one"'s happen. THe most obvious is the old PTBNL. If we get this result from the main piece, we give you this player, if a poorer result, then this player.