If great students of swing mechanics could teach, Tony Gwynn and San Diego State would be pumping out triple crown threats the likes of Mike Trout. Safely, Tony's team has only produced a MLB pitcher of note.
The talent has to be there for starters. Enough to get you either near or on a major league field. If the talent is not there to begin with no amount of Pete Roses or Tony Gwynns are going to help.
And kids with talent sign where? They sign where they think they can get playing time, experience, win and top flight coaching.
Here's a quote from Donnie BB, from his book: "Hitting is Simple-The ABC's of Hitting .300" "I learned more about the mechanics of the swing from Lou Pinella than anyone else I ever worked with-he taught me how the swing works and how to make adjustments". I read in a 1986 or 87 Sports Illustrated article (with Ted Williams, Boggs and Mattingly on the cover) where Ted sat down one afternoon with Boggs and Donnie over beers, to discuss the art of hitting. In that SI, Donnie mentioned back then, Pinella was about the only one who could show him what he was doing wrong, or what and how his mechanics were off, moreso than anyone could. Pinella would literally get in the batters box, to show Donnie such things, Lou led by example, not leaving work for the hitting coach, or even pitching coach...some say Lou was a micro manager, yet I don't see it, or didn't....! The way it was all explained to me aeons ago, (by Ty Cobb and the Bambino) was: Great players like Mantle, Mays, DiMaggio, et al. Don't always make the best coaches. They are the "Naturally talented ones", who don't have to think much how to play exceptionally well, beyond the norm. They are born with talent. Talent they cannot often explain to others. Whereas-those utility players, who spend entire careers on the bench, ie. LaRussa, Cox, Lasorda, Joe Maddon, (yes I said it), and (I despise mentioning Lasorda's name period!!!), Many utility players, or lesser players with lifetime minor league numbers or careers, who turned out to be very good to great coaches, (except Lasorda, pardon me, I'm biased against the dude). Those guys spend their lifetimes in MLB, watching intently and become the best students, teachers of the game. Even when a life of watching and learning never behooves the lack of their own natural talent. One can't always teach talent, one is not always born with talent. Some are, some aren't. While NOTHING is a given, even this rule aforementioned. Yet, it does seem to work that way, with exceptions on both sides of the rule, or belief.... Does that make any sense to you Rick, or did I confuse you more. (I do have a way of doing such you know to well)....hope it helps, my friend...!!