So we've got some young studs with a decent batting eye and really good bat speed. They've shown excellent plate coverage and don't understand why they are slumping. When you press you expand the zone. Simple as that. You must protect an average of three inches outside the black to account for pitches breaking in to the back corners. For some pitchers the break is greater say six to eight inches. You start swinging that far out you are giving the catcher permission to frame a foot off the plate. You have displayed to the umpire that your arc extends that far even if you really aren't chasing that far.
So how do you counter that? First you have to realize when you live on the outside black to hit ; you are out on the end past the sweet spot limiting your power. You are signaling the defense that they need to shift that way. You are lessening the chance you'll make solid contact to begin with when you are out on the end because you are holding the end slightly farther back to make contact at all and starting to commit earlier to compensate. We are talking in thousandths of seconds here. It's enough to disrupt your timing as the umpire and catcher move farther and farther outside.
Common wisdom is to closeup and move up in the box. You know the the curve or the change up is coming because you've held back to defend the back corner. Now they are going to have you lunge on the front foot. you are going to overextend. With your quick bat you'll be ahead of the ball. If you haven't moved up you'll do exactly that. But if they pound the back corner with the slider again you are toast because you are in front of the break and the pitch is too outside to hit. That's how they are setting you up.
I always placed my back foot in the same spot. Always. My front foot could close or open depending on the the pitcher and the pitch. That leads to off axis hitting you say. Yes it does and I used it. To me that's no different than having the coach soft toss into the zone off the foul line. I changed my arc appropriate for the pitch that way. I also limited the length of my arc that way. To counter pitchers and catchers expanding the zone and taking the ump with them; I showed early what I would defend and never alter it. I would purposely foul off pitches that were borderline strikes to a certain place outside or inside.
I'm talking rule book borderline. I narrowed my zone that way. I'd make a statement to the ump by the contempt in my body language for pitches even that close out of the zone. By fouling them off I also let him know I was not going to let him make that call. Other batters would work to erase the batter's boxes. I'd always draw them back in. If the ump objected ; I tell them they were for my reference and not his. You have to make your boundaries clear. Just as you must make clear that you won't let close pitches dictate you.
To me it was a game within the game. As a Right handed hitter when on the road ; I was always trying to hit the brain trust at the near end of the dugout when they pitched me outside. If they were pitching me inside I'd choke up the bat some to protect the handle and shorten the arc. When home : I'd tell my team mates to vacate the far end of the dugout. Take way the outside pitch from a pitcher and you are three quarters of the way to dominating them not the other way around. Have fun and Play Ball!