TomRicardo said:
I mean how often do the Red Sox start the season with their five best starters healthy?
You mean, aside from two of the past three years? (Really, you could argue three of three, depending on how you interpret the situation in 2012.)
First five SPs:
2013: Lester, Buchholz, Dempster, Doubront, Lackey
2012: Lester, Beckett, Buchholz, Doubront, Bard
2011: Lester, Lackey, Buchholz, Beckett, Matsuzaka
You need SP depth because of the possibility of injuries, but you can't count on the DL as a
deus ex machina. There will be times during the year--including, most likely, Opening Day--when all six of the current prospective starters will be healthy, and you'll need a place to put one of them besides the rotation. And since none of our current top six has options remaining, that place will be the bullpen.
You could certainly make a case that it's a better use of resources to pay Dempster $13M to be your 7th reliever than to pay him, say, $7M to be somebody else's 5th starter and get some AAAA journeyman in return, while giving that bullpen slot to de la Rosa or Britton or Villareal. But most likely, those are your two choices. (Well, there's also the option of putting Doubront in the bullpen, in which case you get about three times as many innings from Dempster even though Doubront is clearly the better pitcher of the two.)