The Bill O'Reilly no spin zone approach to Free Throw Shooting

What I don't understand is player's screwing up their Free-Throw Shooting by spinning the ball in their hands. I was working with a Division 1 Prospect yesterday who by the way is an outstanding shooter in a workout and he was only shooting Free-Throws at 70 % clip, I told him to stop and use the no spin zone approach and he proceeded to hit 20 in a row. This is one of those little that help.