There's one thing that you are also overlooking Sabre (and those believing we need to sign two SP's which... we WON'T, book it):
Trading for another starter at the trade deadline.
If it's an absolute must at the deadline, then maybe.
But I still don't think we'll do that, because:
The Org will rely on Wentz coming up by the deadline or Boyd coming back.
They will look at other internal options prior to that: Like Alexander, Fulmer, Faedo, etc...
I'm sorry... but the Tigers are NOT signing two average or better SP's this offseason. You can be as upset as you want to be. It's just not going to happen. Any pitcher we sign beyond one good SP will be suspect/ AAAA/ on a minor-league deal/ Teheran recovery types/ etc.
Which is not a bad gamble to take on those types, and they CAN fill in some needed innings...