Rule sets / OBR / Hidden Ball Trick Balk
Hidden Ball Trick Balk
Not all hidden ball trick attempts are balks but some are.
If there is a runner, or runners, it is a balk when the pitcher, without having the ball, stands on or astride the pitcher's plate or while off the plate, he feints a pitch;
MLB Umpire Development Manual Authoritative interpretation
Official Rule 6.02(a)(9) states a balk shall be called when the pitcher, without having the ball, stands on or astride the pitcher's plate or while off the plate, he feints a pitch. Furthermore, the comment to Rule 6.02(a) stipulates that even in the absence of a "feint to pitch" in the above ruling, straddling the pitcher's rubber without the ball is to be interpreted as intent to deceive and ruled a balk.
This rule is generally enforced during the "hidden ball trick" when the defense tries to deceive the runner regarding the location of the ball in an effort to tag him out. The "hidden ball trick" is a legal play but can only be legally executed when the pitcher is not on or astride the rubber without the ball; however, the pitcher may be in the dirt circle surrounding the rubber.
In addition, if the pitcher places the rosin bag in his glove with, in the umpire's judgement, the intent of deceiving the runner, a balk shall be ruled.