I am copying this post over from the general thread because it shows Whitlock developing new pitches to amplify his already excellent sinker-changeup combination:
From the linked Glob article:
Back in the old PitchFX days, I used to call the bullet slider a Brad Lidge slider, after the reliever who put it to most effective use. Its spin axis is the same as the ball's trajectory, meaning that the spin does not cause any deviation from the initial trajectory. If the batter knows that it is coming, it can be an old-fashioned hanging slider, but if the batter sees the dot, diagnoses a breaking pitch, and expects it to behave like a sweeper, he will extend the barrel too far and stands a good chance of breaking his bat.