Found this:
If the pitcher makes an illegal pitch with the bases unoccupied, it shall be called a ball unless the batter reaches first base on a hit, an error, a base on balls, a hit batter or otherwise. *** An illegal pitch is a quick pitch or a pitch made while not in contact with the rubber. Defacing the ball is illegal but not an illegal pitch by this definition. ***
A ball which slips out of a pitcher's hand and crosses the foul line shall be called a ball; otherwise it will be called no pitch. This would be a balk with men on base.