Bill James believes that with hitters, what you see, is what you get. You just can't teach people to hit. Pitchers, on the other hand, can very often suddenly "get it" and turn the corner. Maybe they change their arm angle, start throwing a new pitch, stop throwing a pitch, lost their velocity but improve their control. There's lots of history of guys like this and even more so when you take into account shifting guys from starters to closers.

But can you teach someone to navigate?