Leaving the leg behind also tends to put the pitcher into a forward-leaning position, which not only hurts speed and accuracy but can also put stress on the pitcher’s back.
Last night, as I often do, I was doing a pitching lesson. The pitcher in question was also doing what many pitcher do – reaching out with her stride leg instead of driving her whole body forward.
That’s a very easy habit for pitcher to fall into. We tell them to get off the pitching rubber, so they throw their stride leg forward to pull them off. The problem is, that often leaves the other leg stuck right where it started – at least until the pitcher makes a conscious, labored effort to pull it into the back leg. That’s one of the things the Queen of the Hill is designed to correct. But you may not always have one of those handy, and even if you do you’re probably not going to allow a pitcher to take it home with her unless she’s your daughter.