Left handed pitcher

Does anyone know what is causing my back foot to drag.

During your delivery, you’re compressing down on you stride leg, while maintaining an upright posture from the waist on up. That back foot dragging is your body’s balance system kicking in and preventing you from lurching forward.

Try this:
during your delivery motion, collapse on the instep of your pivot foot, instead of pushing off on the ball of your pivot foot. Watch how much further you go on down the mound and notice how much more momentum you get off the release. Try and stay with the pitch, instead of being upright and coming down on that stride leg.

Thank you, my pitching coach is saying similar stuff ,but you just explained it a lot better ,again thanks

Keep in mind that, in general, dragging the back foot isn’t a bad thing. Most good pitchers do drag their back foot. In your case, it may appear excessive because, as Coach Baker said, you have a significant collapse of the front leg.

Thanks I have seen several other pitchers drag there foot but mine is a lot worse