There is a thread on BTF about Sabathia’s “numbers,” particularly his BB and K rates, being down this year, as compared to last year, although he is still pitching very well of course.
While the quality of the posts on BTF is nowhere near that of this blog (although they beat us easily in quantity), there are some reasonably intelligent regulars on that site (if anyone interprets that as a dig, it is).
...The thing that people don’t understand (actually one of the things) about regression toward the mean in baseball is that the reason any above or below average player will always regress, on the average, towards average, is that they were not really as good or bad as we thought in the first place, based on any of their stats. That goes for Sabathia, Halladay, Bonds, Chipper Jones, etc., etc. Chipper Jones is not as good as his career stats tell us, even after you do all the appropriate adjustments. Same for Halladay. And Sabathia. And everyone else who has been above average and we think has true talent X. When I say “as we think” I mean as their stats suggest, not as we think based on a credible projection which already does the regression. And of course, there is some chance that any given player is better than his prior stats - it is just that the chances of him being worse is greater than the chances of him being better. That is ALWAYS the case, as long as we properly define the mean for that player.
That is the KEY to understanding regression toward the mean and is what most people don’t understand, even if they think they understand the concept.