Bill James, the godfather of sabermetrics, had one of the longest Q&As I've ever seen with the NYTimes' Freakonomics blog. He answered a ton of reader questions; if you know nothing else about the man, read this
Q: Based on your statistical analysis, how do you feel about the Yankees’ young prospects, namely Chamberlain, Kennedy, and Hughes, making a huge (positive) difference for the Yankee pitching staff?
A: The same as I feel about our young pitching prospects with the Red Sox, really — Buchholz and Lester and Masterson. When you’re depending on young pitching, you’re vulnerable. Some of these guys are going to be very good, but probably not all of them, and there are going to be bumps in the road that will rattle your teeth.
Q: Billy Beane, G.M. for the Oakland A’s, has made sabermetric stats a major part of his "value" philosophy when building a baseball team. He’s frequently said that his method will build regular season winners but it doesn’t seem to work in the playoffs. Do you think that this is simply a result of a small sample size or the wrong statistics being used, or is it something more fundamental about "unmeasurable" statistics, like the ability to perform under pressure and "heart?"
A: Oh, I thought people had stopped asking that. Blast from the past there. Look, there’s a lot of luck in winning in post-season. You’re up against a really good team, by definition, and you’ve only got a few days to get it right. It takes some luck.
Q: It seems that in the field of sabermetrics, there is much more focus on their use in evaluating offensive rather than defensive production; is the reason behind this the fact that the measurement of defensive valuation is less complete in your field?
A: In the 1870’s/1880’s, when the scoring system for baseball games was developed, the statistics invented for batters were well designed and specific, and as such they naturally evolved toward better and better results. The statistics invented for fielders were so awkward and sketchy that they weren’t really very useful, and therefore they never advanced. The official fielding stats today are basically the same as they were in 1885.