This is a good example of a 9-year-old Little League pitcher with very natural but explosive pitching mechanics. This occurs very naturally when pitchers are not over-coached using pitching drills.
When the focus in on using the lower body to provide power instead of just the arm, then even beginner pitchers are able to create an explosive delivery with a long stride and powerful back leg action.
Notice you do not see any slow movements or hesitation which is usually an indication that pitching drills were initially used.
This pitcher displays very good lower body mechanics and with just a couple of adjustments he will be able to improve his velocity, his control while reducing the stress to his arm.
Although his certainly not perfect, I would still be very hesitant to introduce too much to him at this point which might interfere with his natural actions.
This Is A Pitcher That Should Not Be Over-Coached
But remember this, there are no secrets to pitching improvement. Just sound sports science principles that we apply to pitching that just make common sense.