I have a tendency to look at reliever statistics with a jaded eye. While starting pitchers are relatively straightforward in their inning stress, relievers enter games with various levels of stress. While Joe Maddon noted that he likes some relievers to only enter in "clean innings" (no outs, with nobody on), sometimes relievers enter into dirty innings. I doubt enough emphasis is put on the leverage of the situation for relievers. The Cubs game Tuesday had two danger situations for the relievers summoned, and two entirely different levels of performance in them.
A fun read back in the day was Jim Bouton's "Ball Four.