While it hasn't been made official yet, Felix Doubront, not Matt Thornton is likely to make the Red Sox' playoff roster as the 25th man.
What evidence is there for this? First off, it was Doubront, not Thornton who pitched in Wednesday's Red Sox vs. Red Sox scrimmage game, appearing in one relief inning. Then we have the following tweets:
Talking to Nieves it appears as though Doubront will indeed be in bullpen in postseason— Rob Bradford (@bradfo) October 2, 2013
Farrell: "Protecting the downside of something unforeseen happening on the mound" was determining factor on 25th guy, thus likely Doubront.— Ryan Hannable (@Hannable84) October 2, 2013
Frankly, that quote from Farrell makes this whole question of the 25th man seem...obvious.
Jackie Bradley Jr. would be on the roster to take the place of Shane Victorino or Jacoby Ellsbury in the case of short-term injury, but only if both were hurt or the situation called for a defensively-minded starter, since the Sox have generally gone to Jonny Gomes or Mike Carp in left field and Daniel Nava in right when just one was out. Otherwise, he'd be the second pinch-runner behind Quintin Berry.
Matt Thornton would be...well, I guess he'd be the second LOOGY after Franklin Morales? Though, as Brian MacPherson pointed out to me here, opposing managers could really pounce on that by bringing in a right-handed hitter. Yes, Morales has that same vulnerability, but it's never stopped teams from using the LOOGY before, and nor should it.
Doubront, on the other hand? Well, he can give you innings. Imagine a situation where the Red Sox are down big early on--that's a much more realistic scenario than both Jacoby Ellsbury and Shane Victorino being out. The starter is at 100 pitches, and it's just the fourth inning. You turn to Matt Thornton, but how many outs can he get you? Eventually, Ryan Dempster is going to come into the game and record three innings, but then he can't pitch even semi-important innings in games to come. And yes, whether we like it or not, Dempster is actually a decent option in this pen for meaningful outs in, say, the sixth inning.
What Doubront does is provide insurance. The Red Sox can just let him go out there and, if he's ready to do it, eat 70, 80, or maybe even more pitches worth of outs in a blowout. He can save the entire bullpen in a disaster.
Even more than that, though, let's say one of Boston's starters picks up an injury minor enough that they can't make their next start, but aren't done for the entirety of the playoffs. Rather than having to make the dramatic move necessary t replace a player on the playoff roster--one which would leave, say, Jon Lester ineligible for the ALCS should he get injured before Game Five of the ALDS--they can simply turn to Felix Doubront, who seems a much better option than Ryan Dempster for a big game.
There are some who are unhappy with Doubront's seeming reluctance to pitch in relief for the Red Sox, particularly on this "whatever it takes" team. But if Doubront is willing to take on this frankly self-sacrificial role for the team--and it would very much be out of character for John Farrell to tab him for the postseason roster without being perfectly clear about his place first--then there should be no hesitation to include him on the playoff roster.