BAbip is a stat that helps track luck.
A pitcher might make a great pitch, but it results in a weak roller that goes for a hit. If you are star-crossed, that happens often. Another pitcher might hang a curve over the plate, but it results in smash line drive out. If you are fortunate, that happens often. Batting average for balls in play (BAbip) is one measure for discriminating the lucky, good from bad.
We might need a new stat, the "traded for but not mentioned" stat (TFbnm).
Consider the Sabathia/LaPorta trade. A Cy Young winner traded for a prospect. The prospect has been struggling. The pressure is clearly weighing on him.
The fans are screaming that the trade was terrible, because the prospect is not becoming a star.
But here is the thing. The trade was not one for one. The Cy Young winner was traded for multiple players. And more than one of the players received makes it to the big leagues. But because of how the trade is portrayed, they never feel the pressure of providing equal value for the star player.
Case in point, Michael Brantley will be leading off for Cleveland on Opening Day. Brantley and LaPorta were two of four players traded for Sabathia. While this fact is largely ignored in Brantley's case, it is the focus of LaPorta's development.
There should be a stat for that.