I don't buy that 4 games is a sign of a new level of play. How do you know when it's meaningful and when it's just noise?
Is Willie Harris supposed to be this good for the rest of the year?
You realize that these are two different questions, right? Not just because one's in reference to Crisp and one's in reference to Willie Harris, but because one is about finding causes for things we know have happened while the other is about drawing inferences about future results from past results. They're two completely unrelated questions which, assuming they are answerable, must be addressed in completely different ways.
I cannot say that Crisp's stance changes caused
his performance. All I can do is point out the eye-catching correlation
, and note the consistency between the effects those changes are believed to have and the performance on the field. If a hitter is late, lessening the movement and time a hitter needs to get to attack position should
get him to attack position earlier and should
therefore allow him to get better arm extension, which in turn should
enable him to drive more balls. Those changes were made to Coco's stance, and he is driving more balls than previously. It might be a coincidence, but there's reason to think it's not just that.
That doesn't mean Coco Crisp will become a HR hitter with a .350 batting average from now on. It doesn't mean that he's swallowed some magic pill. It just means that of all the little day-to-day problems conspiring against this particular hitter, one has apparently been spotted and solved. There will certainly be more.
Sample size comes into play in mechanics, too. It's the same a tug-of-war between: 1) acting upon limited evidence you have in front of you, and often guessing wrong and 2) waiting for more information to get a clearer picture while performance suffers from your inaction. Experience with particular discipline brings about a certain degree of faith in their substance. Just as Sabermetrician X believes he can find causes or guess at future results with stats, Hitting Coach Q believes he can find causes for slumps or prescribe mechanical changes that will produce results. How do you know when a player's short-term performance is a meaningful indicator of overall performance? I suppose you don't really know it until after his career's over, if then.
But at the professional level, fixes to mechanical problems are almost necessarily
short-term changes to short-term problems.
Say you assume some degree of cause-effect relationship to "proper" mechanics, and there was some hitter who had always been lousy and always been doing something wrong and for some reason nobody ever saw it or commented on it, until one day a good hitting coach found it and fixed it. If that happened, then yes, a previously crappy hitter could turn into a great hitter virtually overnight. The reason that almost never
happens is not because there's no cause-effect relationship to mechanics but because there is
a cause-effect relationship. Hitters and their coaches are looking at mechanics all the time, and fixing small mechanical problems before they become career-determining. This we can assume that Will Harris's performance this season is a result of how he's used, or has some other cause, or is just a statistical fluke that will regress. Harris has been with multiple organizations, one or more of which would have caught his mechanical problems and fixed them. (I suppose he could have just refused to change, or been dumb to the advice he was given, until one day he had some near-religious epiphany and becomes a mechanics nut. But those cases are rare.) You pretty much know that something that totally handicaps a hitter isn't going to be allowed to linger long.
And once hitter coaches are in the game, it just becomes part of the business of practicing. Sabermetrics, still a relatively new field, owes a lot of its popularity to the idea that it could produce big results by looking at the game in a completely new way - or rather a completely new angle on an old way of looking at the game. Those times come in mechanics (Charley Lau) but generally the knowledge is pretty well established, there's not much new, and it becomes less about the mechanics themselves and more about discipline in analysis and finding creative ways to get the same old message across. You can see the same thing happening in SABR as it has become more accepted. The same principles keep coming up again and again: OBP is more important than AVG, sample size is important, a strikeout is just an out for a hitter, K-rates are good predictors of pitching success, etc. Stuff comes to be taken for granted, and there are fewer and fewer groundbreaking insights and fewer and fewer revolutionary developments. But the discipline is still relevant.
I don't know if this answers your question at all, but I enjoyed it.