Rule sets / OBR / Start-Stop Delivery Balk
Start-Stop Delivery Balk
Once a pitcher begins his delivery to the plate he must continue without interruption.
If there is a runner, or runners, it is a balk when the pitcher, while touching his plate, makes any motion naturally associated with his pitch and fails to make such delivery.
MLB Umpire Development Manual Authoritative interpretation
While in contact with the rubber and a runner on base, it is a balk if the pitcher starts his preliminary motion (the stretch) but interrupts that motion before coming set.
If the pitcher is pitching from the windup position, any motion naturally associated with his pitch commits him to pitch without interruption. Otherwise, it is a balk.
Umpires must recognize the difference between the motion to start a delivery and other natural movements pitchers often make (e.g., a pitcher rotates his glove to signal the catcher for another set of signs, he moves his hand to adjust the ball within his glove, straightens up from a bent-knee stance when the catcher requests time).
Video examples
Right-handed pitcher Keone Kela starts his delivery by making a movement with his shoulders and then stops.
Right-handed pitcher Oliver Drake flinches in response to R3's feint to steal home.
Right-handed pitcher A.J. Burnett starts his delivery by lifting his non-pivot foot. He fails to deliver the pitch by making a throw over to first base.
Right-handed pitcher Al Alburquerque starts to come set from the stretch and then stops.
Right-handed pitcher starts a motion and then stops in response to movement by the runner on second base. When the balk is enforced, the runner is awarded third.
Right-handed pitcher starts a motion and then stops with a runner on second base. When the balk is enforced, the runner is awarded third.
Right-handed pitcher starts a motion with his lower half and then stops. He attempts to disenage the pitcher's plate but the balk has already occured. When the balk is enforced, both runners are awarded one base.
Right-handed pitcher stumbles during delivery and fails to deliver the pitch.
Right-handed pitcher stumbles during delivery and fails to deliver the pitch.
Right-handed pitcher fails to complete his delivery when thunder erupts close to the stadium. By the stricted definition, this is a "start-stop" balk.
Right-handed pitcher Homer Bailey fails to complete his delivery after his pivot foot slips.