As far as who the Sox break performer will be, I think that the "breakouts" are going to come from Mookie and Xander building off of last season, and Pedroia and Price doing their veteran things.
Also, I see significant improvements from the trio that stunk last year, Porcello, Hanley, and Pablo. Keep in mind that a significant improvement from a -2 WAR does not mean that Hanley and Pablo will be all stars, but rather 2-3 WAR players.