Balk or Legal

[scrounge]

It's hard to say without seeing it. It would be unreasonable to think that a pitcher has to step back by moving the foot only, with the rest of the body absolutely motionless. So you'd have to judge whether that was just part of stepping off. If you thought it was starting the motion or simulating the motion before stepping off, then yes it would be a balk. But be sure - and be prepared to explain.