Good info. But I guess I view Brogdon and Bellati as locks, and not guys you want to flip-flop/jerk around under either circumstance (the normal course of doing business or to accomodate Song).
So, you've got Alvarado, Seranthony, Kimbrel, Soto and Strahm without options. If Bellatti and Brogdon are both keepers, you are already done. For now the last spot goes to Vasquez or someone optionable. Falter is almost certainly in the rotation and some of those others will stay on starter schedules in AAA.
I don't know that Vasquez is a reason to do it. But if you really want Song badly enough that you'd put either Brogdon or Bellati on the option see-saw, you may as well trade one of them, as their value strikes me as being higher than fungible (unlike Nelson). Heck, perhaps to the Red Sox?
I still think it's odd that they signed Kimbrel and Strahm and traded for Soto.Two of the three would have sufficed. And Brogdon may yet be better than all three of them.