If it can be improved upon over time, then how do you account for the improvement? I think you are giving far, far too much power to the pitcher and not enough to the hitter. It's been the Cubs mentality for a long time. In other words, a hitter doesn't earn a walk, he takes a walk. There is no evidence of that what so ever. When Sosa was great he laid off the outside, off-spped junk. Both before and after he'd swing at it. Just as some things can be learned they can be forgotten. Improvement comes from age, experience, trying to improve an eye at the plate comes from learning what works and more importantly what doesn't work. Pitchers only adjust when a hitter becomes great, obviously they initially adjust to the rookie's strengths/weaknesses at the plate, but once that's established unless something happens like it did for Sosa, it stays the same. That's not giving too much credit to the pitcher, that's the exception to the rule. There are much better ways to allocate time than trying to get dramatic changes from a 25yo hitter that has been conditioned to be overly aggressive his entire career of playing ball. That can be improved, but nothing beyond standard progression that every player typically goes thru.