Can a Pitcher Speed-Up His Windup to Catch Runner Stealing Home?
If a pitcher is in the full windup and the runner at 3B breaks towards home, the pitcher may speed up his windup to deliver the ball to the catcher to try to retire the runner. However, the pitcher must keep all of the components of his delivery intact.He may not simplify his motion to step and throw just to get rid of the pitch quicker. This is a balk.
Once the pitcher begins his windup with a step backward with his stride foot, he must complete the pitch to the plate. He may not step off or stop his windup midstream and throw to the plate.
The pitcher should check the runner at 3B prior to starting his delivery to avoid giving the runner a big jump and then risk altering his delivery to catch the runner at the plate. It is okay to speed up his delivery but not alter his delivery.
This is a judgement call for the umpire.