We want a pitcher, not a belly-itcher!
A pitcher scratching his tum instead of throwing balls indicates a lack of focus and engagement with the game. A solid, by-the-books jeer.
We want a batter, not a broken ladder!
A nonsensical metaphor. The reference to a ladder clearly exists solely to make the rhyme work, and the rhyme itself only exists in reference to the above. Awful jeer, no substance whatsoever.