Checking out this Run Differential stat

If anyone has seen this before, let me know, before I start to get excited. Here, what we do is to consider the score when the pitcher entered the game, and consider the score when they left, and come up with a +/- for runs. The offense obviously has something to do with this, so I realize the outside forces on this examination, but still...

Let's start with the rotation, who have all "enjoyed" six starts:

Oswalt: -4
Wandy: -15
Myers: -1
Norris: -18
Paulino: -15

And now the bullpen:

Sampson: -3
Fulchino: -8
Byrdak: -2
Moehler: -10
Lopez: -2
Gervacio: -6
Chacin: 0
Lyon: -6 (although it should be noted that, in his last eight appearances, he's at 0)
Lindstrom: -3

This is admittedly biased towards the starters, and the limitations of the offense, which for our chosen team, is a heavy bias.