I have been a professional pitching instructor for 15 years. Youth, HS and College coach. I played AAA with the White Sox. I would say the the toughest fix is when a pitcher over rotates the lead foot. This happens because of “flying open” " rushing" etc. The 3 most important things to work on as a pitcher are direction, staying back, and following through with good arm extension. NOT bending your back… any suggestions, out of the box drills to correct the over rotation. I have a RHP whos tows are at about 11 o’clock striking with his heel. He is very athletic and has no restrictions with hip mobility. Thanks.