Originally Posted by RedsManRick
I remember reading a debate once, perhaps in the Neyer/James Guide to Pitchers, about what defines a pitch. Is it defined by how it is thrown or how it moves? Pitches aren't so discrete and consistent in how they behave that such perfectly MECE (mutually exclusive, collectively exhaustive) labels work.
Is it possible that he is throwing the ball using the grip of slider but doing something different with his wrist/release such that it causes more vertical break than it used to?
There's always been talk about Arroyo basically inventing pitches as he goes -- same with many of the Japanese pitchers. Why does it have to be one thing or the other? Why not just say that he throws a breaking ball that tends to move a certain way and be done with it?
That's absolutely possible -- he might have a slider grip and thinks he's throwing a slider, but it's actually more of a "slurve." (It's definitely not a true curve.)