Even More Bonds Data
I love baseball-reference.com. In the comments to my post on Bonds, I suggested that it would be interesting to look at a bunch of players and see how they performed after the age of 34 (the age when Bonds began his relationship with trainer Greg Anderson). Sure enough, poking around on baseball-reference.com, I found what I was looking for. In the section on each player card regarding "similarity scores" there is a link for "Compare Stats" that gives you this page, which compares Bonds to the most similar players to him for his career. You can then compare them for any particular age, such as 34.
Let's take a look at the percentage increase or decrease between these players' OPS+ (OBP plus SLG adjusted for league and park) in the years before age 34 and after, sorted by their pre-34 OPS+ (I need SuperNoVa's table creating skills) [SNV - You got 'em]:
|Player||Pre-34 OPS+||Post-34 OPS+||% Change|
It's more revealing as a bar graph, but I don't have time to put one together, and you get the picture. As I suspected, Bonds' dramatic improvement is unmatched by any of the great players with close similarity scores. Indeed, it's not even like Bonds' increase is more than others -- it is diametrically opposed to what the other greats did in their later years. All but one show decreases, where Bonds shows a dramatic increase. Even Aaron, who was very productive in his later years, decreased.
Interestingly, Rafael Palmeiro has managed to stay even in his post-34 career, but he is still far below Bonds' improvement. (Rafi, as we know, apparently takes another substance for "growth", which is legal with prescription.) I think he may be a good example of how better (legitimate) conditioning and preparation can help today's players maintain performance in their later years, but not increase them dramatically. It might also simply reflect the general increase in offense during the recent period.
It would seem there is some statistical analysis well-beyond my skills that would show how such a disparity is very very very remote.