Playoff rosters tend to be more arbitrary than regular season 25-man rosters. During the regular season, an American League team generally rolls with 5 starting pitchers, 7-8 relief pitchers, 9 starting position players (including DH), and 3-4 bench players. However, because of the more regular off days in the postseason, a team can play with only 4 starting pitchers and 9 position players, leaving plenty of room to play with the rest of the squad. This leaves 12 players to make 25, and every team’s preferences toward bench players versus relief pitchers usually makes the difference.
First, let’s count out the players who will definitely make the roster. Among the pitchers: Craig Breslow, Clay Buchholz, John Lackey, Jon Lester, Jake Peavy, Junichi Tazawa, Koji Uehara will all be on the playoff roster. Those are four starting pitchers and three relief pitchers. Among the offensive players: David Ross (C), Jarrod Saltalamacchia (C), Xander Bogaerts (SS/3B), Stephen Drew (SS), Will Middlebrooks (3B), Mike Napoli (1B), Dustin Pedroia (2B), Mike Carp (1B/LF), Jacoby Ellsbury (CF), Jonny Gomes (LF), Daniel Nava (LF/RF), Shane Victorino (RF/CF), and David Ortiz (DH) will all definitely make the playoff roster. Those are nine starting players and four bench players, leaving a total of five spots that are totally open.
Now, a team cannot work with just three relievers so we can reasonably expect two or three more on the playoff roster. Candidates for those spots are Drake Britton (1-1, 3.86), Ryan Dempster (8-9, 4.59), Felix Doubront (11-6, 4.08), Franklin Morales (2-2, 4.62), Matt Thornton (0-4, 3.56), and Brandon Workman (6-3, 4.97). That’s not a hugely appealing group of names, as it ranges between rookies and guys who have started pretty much all season with the only established reliever on the list being Matt Thornton. Britton and Workman have been going through some struggles lately, and their inexperience could be a problem in the playoffs, while Morales has been dominant lately. Because of this, Thornton and Morales should make the roster; however, they are both lefties leaving Ryan Dempster, who has come out of the bullpen once this year, as the only righty remaining. He does have experience in the bullpen, however, and could be a useful arm.
If the Red Sox do choose to employ six relievers in their bullpen, then that leaves the Red Sox with two open spots on their bench. Between Bogaerts, Carp, Nava/Gomes, and Ross the Red Sox have players who can back up any position except center field on their bench. Thus, they should consider a defensive replacement/pinch runner and the choices are Jackie Bradley Jr. (.189/.280/.337) and Quintin Berry (.191/.309/.257 in Triple-A). Neither one has really adjusted to major league pitching yet, but Berry provides a skill set that Bradley Jr. really doesn’t and that’s the role of a pure speed guy. In his career, he has successfully stolen 23 of 23 bases and with his passable defense, he provides value that Bradley Jr. really doesn’t. However, the Red Sox would still have a bench spot open and Bradley Jr. has more of a case to make the team than Brock Holt, Brandon Snyder, or Ryan Lavarnway so he could still make it on as a guy who might never play but could soak up the playoff atmosphere.
Altogether this leaves the Red Sox with a playoff rotation of Jon Lester, Clay Buchholz, Jake Peavy, and John Lackey; a playoff bullpen of Craig Breslow, Ryan Dempster, Franklin Morales, Junichi Tazawa, Matt Thornton, and Koji Uehara; a playoff lineup of Jacoby Ellsbury, Shane Victorino, Dustin Pedroia, David Ortiz, Mike Napoli, Daniel Nava/Jonny Gomes, Jarrod Saltalamacchia, Stephen Drew, and Will Middlebrooks; and a playoff bench of Quintin Berry, Jackie Bradley Jr., Xander Bogaerts, Mike Carp, Daniel Nava/Jonny Gomes, and David Ross. Regardless of how the final few spots turn out, that looks like a team that can go all the way.