Assuming that all five starters make the playoff roster and that Maddon carries 11 pitchers going into the playoffs (like he did last year). Who are the 6 other pitchers?
Assuming everyone is healthy, Chapman, Rondon, Strop and Wood are locks. So the last two come from a pool of Cahill, Edwards, Grimm and Montgomery.
Cahill has been the most consistent this year, is versatile in that he can go long or short, and performed very well in the playoffs last year. I have to assume he has one of the slots.
Edwards has been amazing good except for that one blow up against St Louis. I have to wonder, though, whether Maddon trusts him in high leverage situations yet.
Grimm and Montgomery both got off the rocky starts, but have been absolutely lights out over the last month or so. They're the two most talented options, and are sort of right/left mirror images of each other.
If I had to guess right now, I'd guess it would be Cahill with Grimm over Montgomery since you probably don't need a third lefty in the pen. I could also see Maddon choosing to go with a 12th pitcher instead of a marginal left handed bat at the end of the bench (Coughlin or Montero).