I was just thinking about this earlier today and I thought I would toss it out here to start some discussion.
Plate discipline is something that is integral to a baseball player. There are many reasons for it. First, the closer the pitch is to the center of the plate, the more likely a player is to punish that pitch. I am sure 90% of us are familiar with the Ted Williams batting average chart of the strikezone posted below:
Now that chart is just an idea, but I think that for most hitters, it holds true at least in theory, that the same hot zones are in the same areas. So choosing to swing at pitches in the strikezone is going to make you a better hitter than if you choose to swing at pitches outside of the strikezone or on the fringes.
That idea goes hand in hand with walks. The fewer pitches outside of the zone you swing at, the more walks a normal player will have (some guys simply make a ton of contact, so their walks are going to be low because they are hitting strikes more than most guys are) or at the very least, the fewer strikeouts a player is going to have. Both things are likely to improve a players batting average, which in turn improves a guys OBP and SLG.
Now, there have been studies out there that have shown that players who don't have good plate discipline (in terms of strikeout to walk ratio, since we don't have pitch location data for the minors at all and only for a handful of seasons for the Majors to work with) typically do not develop it as they get older.
I had a few thoughts running through my mind while thinking about this though.
1. OBP hasn't really been a focus for most teams for that long of a period of time. Neither have advanced numbers or understanding of how a player got his numbers (the use of BABIP along with HR's, walks, strikeouts and sac's to determine a players predictable average). Does that have something to do with the data suggesting that players can't develop it? If guys were able to use their raw talents in the minors to hit for a strong average despite swinging at questionable pitches too often lead to teams not emphasizing them to be more selective because they had put up a good average?
2. There are multiple types of poor plate discipline. Some guys are just very aggressive in the strikezone. Some guys expand the zone because they think they can be Vlad Guerrero. Some guys simply can't identify pitches well enough and think they are swinging at strikes but then the ball breaks out of the zone.
3. Looking back at thought 2, which of those can be taught? I think that the guys who are aggressive within the zone but don't chase but still have poor K/BB rates simply don't have the bat ability to be every day players. If you can't hit pitches within the zone well enough, it isn't likely fixable. Guys who expand the zone because they think they can hit anything.... can that be fixed? How would you go about it? I personally do think that it is fixable, as long as the reason they aren't expanding is because they lack the ability to identify the pitch often. If the problem is pitch recognition, is that fixable? How would you go about it? I think that in most cases, it is something that can be taught. Somewhere along the line, the guys who have that ability learned it. Yes, some guys do have better eyesight than others, but I think that all of these pro players should have the eyesight to accomplish this. The key here is figuring out how to improve a players pitch identification.
So, those are some initial thoughts from me. What about you guys? I think this is a really interesting topic of thought. I would love to hear everyones opinion on it.