I should clarify. SP get injured quite frequently. And the effect of those SP is much, much greater on the overall performance of a team than that of a LOOGY or a middle reliever. The fact that the Sox have at least 2-3 guys who can close makes even losing a back end guy fine.
You're counting on Pettitte to give you something he hasn't given you since 2009. You say he pitched well last year, but he threw against a bunch of s*** baller teams. He faced:
CIN (21st in RS)
CLE (22nd in RS)
KCR (20th in RS)
LAA (Threw 7 IP, 5 ER)
MIN (16th in RS)
NYM (2x) (25th in RS)
SEA (27th in RS)
TB (18th in RS)
TOR (2X) (13th in RS)
WAS (10th in RS)
He faced two top 10 offenses, and got plowed by one of them. If you want to count on him, fine, but his line last year was very misleading considering his opposition. Again, he hasn't thrown 130 IP since 2009, and when he did, he had a 4.16 ERA. That's pretty consistent with what Dempster will give you.
Kuroda, fine, but Buchholz can be just as effective as Kuroda. In fact, after Buch shook off the rust from behind his ears last year, he and Kuroda basically went tit for tat from May through September (Buch: 3.19 ERA, Kuroda: 3.28 ERA).
You talk about Doubront being out of shape, but completely ignore Hughes having a bulging disc. That sounds about right. Plus, Doubront had much better peripherals last year than Hughes.
Nova got plowed last year.
And the Sox are much better prepared for when the injuries hit.
With CC leading the way, the Yankees probably have a better rotation than the Sox. But #2-5 are comparable.