I assume that this thread is for the ALDS, as the ALCS/WS rosters could be slightly different. I would expect Cora to keep more pitchers on the roster in the later series. I also assume that I this thread is for what will likely happen, not what we want to happen.
OK, let's start with what should be 13 obvious and undebateble locks to anyone that has any remote interest in this team (the numbers such as SP1, UT2 should be ignored):
1B: Moreland
2B: Kinsler
SS: Bogaerts
OF: Benintendi
OF: Betts
OF: JBJ
DH: JDM
3B: Nunez
SP1: Sale (assuming good health)
SP2: Price
SP3: Porcello
SP4: EdRod (assuming good health)
RP1: Kimbrel
For the rest, I'm going to assume that Cora keeps 12 pitchers for the ALDS. So, I'll start with 8 "likely's". These guys are probably on, barring a major regression in performance or injury:
C: Sandy Leon. Probably the most at-risk of this group for being left off, but I don't see Cora benching the guy that's been their primary catcher all season.
UT1: Former MLB All Star Brock Holt!!
UT2: Steve Pearce
RP2: Barnes. Some of his mid-season correction was due to BABIP regression. Hopefully he got the home runs and aches and pains out of his system.
RP3: Joe Kelly. BABIP caught up to him a bit in August as well. I think Cora knows the game threads here will explode when he comes in, so he'll be on just for that reason alone.
RP4: The appropriately monikered Workman
RP5: Brasier. He's earned it, but his track record is miniscule, so this could still change.
RP6: Poyner. A lefty out of the pen is always a good idea. Pomeranz, OTOH, isn't.
Now my best guess for the remaining 4 slots:
C2 & UT3: Swihart. I'd say this is the most interesting position battle, and this one really could go either way. I'll venture Swihart as he does bring some additional utility capability.
UT4: Brandon Phillips. I could just as easily see Vazquez as C2 and Swihart taking this role, however. Or Devers.
RP7: Steven Wright. I think he really brings a different angle, and there's still time to stretch him out a bit for him to be a 1+ to 2 inning guy.
RP8: Eovaldi. He's shown just enough in his good stretches that he can fill the early inning relief role. OTOH, he's the most likely to sit if Cora goes with 11 pitchers.
The following are the guys most likely to make the roster if the any of the above don't make it for whatever reason (injury, manager decision, etc.):
C: Vazquez. See above.
3B: Devers. I'd say that Swihart, Vazquez, Phillips and Devers are in competition for 2 spots (3 if 11 pitchers).
P: Brian Johnson. Slight edge over Velazquez, but could go either way. I'll slot him as the first injury recall among the pitchers if a starter goes down.
P: Velazquez. See above.
RP: Hembree. Probably needs an injury or a major regression from Brasier.
RP: Robbie Scott. Ditto, except he's Poyner's backup at this point.
The following guys are almost certainly not sniffing the post-season, barring a disaster elsewhere:
IF: Tzu-Wei Lin
IF: Sam Travis
P: William Cuevas
P: Drew Pomeranz (please make this so, Alex)
P: Tyler Thornburg. A shame, but let's see how he responds after a normal and hopefully healthy spring training in 2019. I guess he could still end up ahead of Hembree in the depth chart, pending how the remaining 3 weeks go.