According to the Official Baseball Rules (OBR), the pitcher, after coming to a set position, may either deliver a pitch, step off the pitching plate or throw to ANY base. As the rules are written, you can throw to 1st base while your foot is still engaged with the pitching plate as long as you step directly towards 1st base without any deception to the runner. Technically, all pick off moves must be made by stepping directly to the base while still engaged with the pitchin plate (rubber). The jump step, while disengaging the pivot foot from the pitching plate, is technically a balk but has evolved as still being in contact with the pitching plate, thus allowing it to be an accepted move to coincide with the OBR pitchin rules. I read this recently in the OBR and found it to be contrary to everything I knew about pick off moves to first base. I'm sure I will get a lot of resistance on this posting, but read the OBR and give me some feedback on interpretation. I have attached the exact wording for your convienence.
The Set Position. Set Position shall be indicated by the pitcher when he stands
facing the batter with his pivot foot in contact with, and his other foot in front of, the
pitcher’s plate, holding the ball in both hands in front of his body and coming to a
complete stop. From such Set Position he may deliver the ball to the batter, throw
to a base or step backward off the pitcher’s plate with his pivot foot. Before
assuming Set Position, the pitcher may elect to make any natural preliminary
motion such as that known as “the stretch.” But if he so elects, he shall come to Set
Position before delivering the ball to the batter. After assuming Set Position, any
natural motion associated with his delivery of the ball to the batter commits him to
the pitch without alteration or interruption.
At any time during the pitcher’s preliminary movements and until his natural
pitching motion commits him to the pitch, he may throw to any base provided he
steps directly toward such base before making the throw.
Rule 8.01(c) Comment: The pitcher shall step “ahead of the throw.” A snap throw followed by
the step directly toward the base is a balk.