Next time you watch him......when he first steps on the rubber before every pitch, before he looks at the sign from the catcher he puts his hand on the ball in his glove in a very strange position (split finger). Then, if the catcher calls for the splitter, nothing else happens and he pitches.
But if the catcher calls for another pitch (fast or change are his two others I believe), then he has to maneuver his hand behind his glove, and it shakes his whole glove when he does this. You don't have to be at a side-angle to see it.
So that means that hitters should be able to know if a splitter is coming....and they should know if either a fastball or changeup is coming.
Until he fixes this, I don't think he'll be consistent. I assumed that this was the reason he was sent to the minors, as the Red Sox figured out how to read what was coming....but apparently they didn't even work on this?