[Welpe]

Hi Matt, welcome to the forum and thanks for your question. I can see that Bob beat me to the punch while I was composing my answer, none the less...

Here is rule 8.01(a) from the Official Baseball Rules:

"The Windup Position. The pitcher shall stand facing the batter, his pivot foot incontact with the pitcher’s plate and the other foot free. From this position any natural movement associated with his delivery of the ball to the batter commits him to the pitch without interruption or alteration. He shall not raise either foot from the ground, except that in his actual delivery of the ball to the batter, he may take one step backward, and one step forward with his free foot."

Natural movement only applies in identifying when the pitch starts. There is no requirement that the pitcher completes a "natural" or "normal" windup, only that once he starts a natural motion to pitch, he is committed to pitch.

In other words, once the pitcher begins his motion from the windup, he can hurry it up and make what essentially looks like a regular throw to the plate. This is still considered a pitch and the batter is still entitled to hit it.

Thank you again and please feel free to stick around.