There are many key factors in the Pitching Delivery but arguably the BACK LEG being the most important since this is the starting point of the delivery…every other body part moves off the back leg. The back leg plays a big factor in both control/accuracy and velocity as you will see below.
Here are the two key reasons as to why the back leg is so important:
The back leg will determine your body control down the mound and could ultimately decide how balanced you are when your stride foot lands. To have total body control and balance going down the mound a pitcher must move from his back leg completely sideways without any rotation left or right on his back leg. A pitcher will notice they are moving 100% sideways by feeling their body leave their back leg on the inside of their back foot, rather than leaving their back leg from their big toe. There is a huge difference when a pitcher figures this out and can consistently move their body off their back leg an feel pressure on the inside of their back foot. This creation of a 100% sideways motion helps a pitcher maintain complete body control (provided other body parts are in control) and therefore increase their control and accuracy around the plate.
Velocity starts with how the pitcher gathers himself over his back leg and then how their back leg performs when the body starts to move forward from the back leg. During front leg lift the back leg should be in a slightly bent position. When the body starts to move away from the back leg, the back leg should stay in this slightly bent position and not convert to a “collapsed” position, which would be closer to 110dgr’s. Once a pitcher peforms “back leg collapse” the body will slow down and therefore move slower down the mound creating less momentum and arm speed to produce maximum velocity. The back leg needs to stay slightly bent when the body moves away from the back leg so a pitcher can maintain momentum down the mound and produce maximum arm speed which results in maximum velocity. The further a pitcher collapses his back leg the slower he will move down the mound!
To see these motions happening with the back leg a coach will need to sit in front of the pitcher (that’s right, in front of the pitcher) and may need the help of video since these motions happen very quickly.