As I work with my students on developing strength in there legs for better balance and more power, I find that most cannot get the weight from the right side to a solid left side. Resulting in a swing that hangs back, with the players momentum going away from the target rather than moving toward the target. If we picture a circle, imagine the outside of the circle as the club head path. The center of the circle is obviously around the middle of your belly. if you can visualize what the club head path would do if the center started to move backwards before the club path got to the bottom of the arc, You can see this will cause the club head path to be altered.