Covering the Front and Back Pages of the Newspaper
March 16, 2009
BASEBALL: EWSL 2009 Age and Rookie Baselines
It's time once again for my annual division previews using Established Win Shares Levels, which are explained here. Before we get to rolling out the 2009 EWSLs, I have to update the age adjustments and rookie values I use. These are based on the data I have gathered over the past five seasons, and so with each passing year, one would hope they become progressively more stable and useful (how accurate EWSL was in 2008 is another day's story, but of course as I always remind my readers, EWSL doesn't predict the future, it just provides a rough count of the talent on hand).
As you can see, there were the usual annual variations from historic norms, but the overall 5-year results are still pretty stable, showing that non-pitchers as a group improve rapidly in their early 20s, more slowly in their mid-20s, and begin a remorseless downward slide starting at age 29, with ages 35 and 37 being the worst culprits on the south side of 40 for one-year decline (if anything, the aggregate numbers conceal the extent of the decline because of people dropping out of the sample - note that a third of the guys who have jobs at age 30 are gone from the preseason depth charts by age 33). The interesting question is whether these trends have been skewed by steroid use; I note that in 2008, the decline rates for hitters in the age 31-34 bracket and the age 38-and-up bracket were unusually steep by historic standards. (The 35-year-old cohort was extremely small this year due to a lot of guys hitting the wall early). It was also a rough year for 23-year-olds, but that seems more like random noise.
I've included, for the first time, a total line for all ages at the bottom, and you can see that the average non-pitcher comes up 6.4% short of established levels in any given year. When you think about it, that's not really surprising.
The pitchers are by nature more volatile - you will notice that the average pitcher is apt to be off closer to 10% over the 5-year period. It was a freakishly good year for 23-24-year-old pitchers, as well as age 31 and age 39 (the latter being basically Mike Mussina), and crummy for everyone else; the age 28 and 34 groups, already smaller than their surrounding age cohorts, got slaughtered. The overall 5-year pattern remains one of decline for pitchers in every age group above 26, with brutal attrition rates beyond age 32. Pitching is rough business.
The rookie adjustments remain, along with the ad hoc fudge factor, the most glaringly unscientific part of this enterprise, but I need some less than wholly random way to plug in the rookies, and at least for everyday players the rough guideline that has them around 11 Win Shares a year for rookies with everyday jobs mostly holds up. Rookie starting pitchers, of course, will break your heart.
Posted by Baseball Crank at 9:22 AM | Baseball 2009 | Baseball Studies | Comments (0) | TrackBack (0)