I'm in that boat too. I don't think Theo will ultimately deal for Darvish, but look at what a rental like JD Martinez brought back. He was about a 1-1.5 WAR improvement for the DBacks and they gave up nothing outside of Dawel Lugo. So, even while assuming that a front line SP will be a little more valuable because you can adjust his usage more than a position player, Darvish won't cost someone off the 25 man roster.