When MLB channel wasn't talking about Tebo and the Jets , they had a saber guy on who was talking about how defense is vastly underestimated in its effect on pitching, mainly because it hasn't been quantified as well yet. But he said that's happening now, and they are finding defense is more important than originally thought--in terms of runs allowed, how much the bullpen is used, etc.
It strikes me that one of the Red Sox main problems is their neglect of defense. The lack of range, for example, last year on the left side of the infield. The outfield defense--Crawford wasn't great at Fenway in LF. And RF defense was average. And their defense against stolen bases was nada. So how much of this had an effect on their pitching, in terms of runs allowed and bullpen use? I doubt the front office or Tito ever bothered to ask.