It’s extremely important to pitch using the information a batter provides.  On a basic level, this is just understanding what a foul ball means.  If you throw your best fastball down the middle, and the batter fouls it off to the opposite field, he is late.  If he pulls that same pitch, he is early.  To the batter who is late, you force feed him your fastball and move it in on his hands if he starts to catch up.  If he is early, it’s probably time to show him an offspeed pitch. 

By giving a late hitter an offspeed pitch, or something away in the zone, you’re doing him a favor by accommodating his inferior (in respect to your velocity) batspeed.  By throwing offspeed to the early hitter, however, you are exploiting the fact that he is not keeping his hands back long enough in the zone.

However, there is more to it than just this early or late judgment.  One has to watch the hitter and ask himself, is this batter truly showing that he has a fast bat, and is waiting til the ball gets deep in the zone before he swings, or is he just cheating, and jumping at the pitch to cover up slower hands? 

A jumping, cheating hitter will shift his weight forward early and often pull his head and stride foot toward the line. If you see this, its time to make that hitter prove himself, which is best accomplished by busting him in as hard as possible.

Throwing offspeed would work if he jumps again but chances are, if you’re pitching against good competition, this hitter knows not to jump, but does it on occasion anyway to try to steal an extra base hit.  Throwing offspeed to this hitter would be a favor.  I would rather err on the side of aggression here, especially if this hitter isn’t in the heart of the lineup.  Being aggressive and making a hitter prove his worth on the inside part of the plate is something I like to do if it looks like a hitter is trying to cheat against me.

But the hitter who pulls you foul who waits til the ball is deep in the zone, keeps his head on the ball, and strides straight or in to the plate is one with a good bat, who has you well timed.  This hitter would be farther out in front of offspeed, and would have trouble keeping his very quick hands back.  Its a good idea to challenge these types of hitters in with fastballs as well, as long as you get it in far enough.  The farther in a pitch is, the farther out in front of the plate a batter must hit it to put it in play, if he is to get barrel on it.  A good inside fastball can be impossible to hit in play with authority.   They might rip it foul again, but if they do they are only further setting themselves up to for failure against a good offspeed pitch, and if they are late they will hit a 15 foot nubber back to you.

Reading hitters takes sharp perception, but it’s an essential skill to learn.  Pitch selection is not always black and white, so take what information the batter provides and use it against him.  If all else fails and you’re not sure, don’t be afraid of contact, be aggressive, and make a hitter prove himself.