What Roger said, plus this extra bit from recent personal experience:
My son is a 15 yo RHP, with a pure sidearm delivery. There is nothing “low 3/4” or “submarine” about it: The kid is a sidearmer and has done very well as a pitcher at each new competitive level.
Right now he’s pitching/playing in an 18U Fall Ball league and he’s facing better hitters than he was used to, as well as trying to hit better pitching than he’s used to seeing. He might be pressing a little in order to prove that he belongs at this level.
For awhile now, his delivery has included a substantial reverse rotation of his torso going into leg lift–but lately he has been rotating so much that the hitters get a full view of his numbers before he strides forward.
This has several consequences–the one he wanted (and got) was that some hitters are pretty nervous when they see that delivery–especially righties.
The consequence that he didn’t want is: His command of the strike zone is not nearly as good as it used to be.
I probably should have seen it coming sooner, but it took awhile to sink in: Video clearly shows that when he reverse rotates his torso to “show his numbers”, his eyes and head are far off the target–basically at the farthest point of this reverse rotation his face is pointed toward 3rd base.
Then he goes into his stride and his hips open, then his upper torso/shoulders open–but, again, video shows exactly what is happening: His eyes and head should have been tracking forward in a straight line to the target from the earliest part of his delivery, but they don’t…instead he must rotate his head through almost 90 degrees of angle (from 3rd base to HP) to get on track to the target and his eyes then track forward to the target very late in the delivery. It is very hard to reliably pick up the target off of that kind of head movement.
We talked about it just last night, because he again had mixed results in a Sunday game–when his pitches were in the zone it was awesome but he couldn’t reliably control the zone and he was missing inside/outside a lot. He is going to eliminate that exaggerated reverse rotation in his delivery, because there is no physical way he can keep his head on a stable track toward the target when he does that.
He doesn’t keep up on all the drills he probably should be doing but last night we got very good results with the towel drill in our front room. We talked about focusing on the target and then not rotating so far backward that his head/eyes would ever come off of the target. When he kept the target in complete focus throughout his delivery, the towel drill worked perfectly. When he fell back into his habit of too much reverse rotation he was erratic again–so that was good feedback.
We both are feeling very confident that his command will return shortly…