What analogy does Spinelli use when describing Grayson learning to read?

Spinelli uses a baseball analogy..... and what could be more fitting for Grayson.

The old man showed an early knack for consonants. Sometimes he got m and n mixed up, but the only one that gave him trouble day in and day out was c. It reminded him of a bronc some cowboy dared him to ride in his Texas League days. He would saddle up that c, climb aboard and grip the pommel for dear life, and ol' c, more often than not, it would throw him. Whenever that happened, he'd just climb right back on and ride 'er some more. Pretty soon c saw who was boss and gave up the fight. But even at their orneriest, consonants were fun.

Vowels were something else. He didn't like them, and they didn't like him. There were only five of them, but they seemed to be everywhere. Why, you could go through twenty words without bumping into some of the shyer consonants, but it seemed as if you couldn't tiptoe past a syllable without waking up a vowel. Consonants, you knew pretty much where they stood, but you could never trust a vowel. To the old pitcher, they were like his own best knuckleball come back to haunt him. In, out, up, down -- not even the pitcher, much much less the batter, knew which way it would break. He kept swinging and missing.

But the kid was a good manager, and tough. He would never let him slink back to the showers, but kept sending him back up to the plate. The kid used different words, but in his ears the old Minor Leaguer heard: "Keep your eye on it . Hold your swing . Watch it all the way in... Don't be anxious...Just make contact."