At the end of the day, the problem with the rotation is its lack of a #1. At best, Lester is a 2 and Buchholz will never be more than a 3 due to his durability issues. Adding a #4 in Dempster was meaningless.
All last year, we heard that Lester would get better because of his FIP. He was "unlucky" even though teams were teeing off on him. Well, maybe he's not much better than a 15 W 3.8 - 4.2 ERA guy. He's a fine pitcher, but not a leader and not a #1.
Until the Sox improve the front of their rotation, they won't be a playoff team.