Let’s talk about the aging process in baseball, and how it relates to anabolic steroid use. Simply put (absurdly simply) there are two processes at work in a player’s career; for simplicity’s sake, let’s call them athleticism and skill. A player’s athleticism probably increases slightly early in a baseball career, but by the age of 25 or so it’s peaked. (There is some variation, of course.) A player’s skill, on the other hand, tends to increase throughout his career, with the exception of someone like Shawon Dunston, or (perhaps, we’ll see) Jeff Francoeur, whose skills flatline early on and never improve. Again, this is a simplification. For instance, strength tends to improve well into the thirties, barring injury, so it’s part of “skill” by this definition, but you wouldn’t normally think of it this way.
What steroids do — what they are prescribed to do, what their medical purpose is — is to aid in recovery. In an athletic context, what people mostly notice are the showy muscles and added bulk. It is unclear, still, how much this helps in baseball. Maybe the home runs go further, and a ball off the wall goes over the fence. Maybe. And see above about getting stronger as you age; players like Hank Aaron and Willie Mays got a lot bigger as they got older, too. But at the same time, what anabolic steroids are intended to do can easily help. The players who have seemingly enjoyed the biggest boost from steroid use haven’t been scrubs who suddenly got better; they have been either aging stars like Barry Bonds, Mark McGwire, and Rafael Palmeiro, or talented players who hadn’t put it all together yet like Sammy Sosa.
One of the terms for the areas where these players have done the most damage — home runs and walks, for the most part — is “old player’s skills”. Players have always tended to hit for more power as they’ve gotten older, and always tended to draw more walks. There are a number of reasons for this, including increased strength, but also greater knowledge of what is and isn’t a strike, and of what pitches a player can hit with authority. At the same time, these have been offset by loss of speed and batting average — “young player’s skills”. At a certain level, the decay in young player’s skills is too much for the increased old player’s skills to overcome; usually, the player loses the ability to make contact often enough to hit for power. One of the discoveries since James invented these concepts has been that players with young player’s skills — Sosa would be a good example — tend to last longer than players with old player’s skills. They have both more room to rise and farther to fall.
So far, little enough has happened to keep these players running well. Bonds and Sosa were fast guys who eventually got really slow; McGwire and Palmeiro were slow guys who got slower. But what these steroid users have found is that they’ve arrested, or even reversed, the decline in their contact rates and batting averages. Bonds, for example, had in the first half of his career a fairly normal pattern in which he peaked around age 28, then started to lose a few points off his batting average, only to see it start to rise again when he started serious steroid use around age 35. McGwire added batting average as he got older; his three highest full-season averages were in his last three full seasons.
This is historically much more atypical than their home run surges. Willie Mays, for example; he hit his career high in homers at 34. Aaron hit his at 37. But Mays, who won a batting title at 23 and was a career .315 hitter at 32, hit .300 only once after that age and saw his career batting average fall by ten points before he retired. Aaron won two batting titles, at 22 and 25, and was a .320 hitter when he moved to Atlanta at age 32; he hit .300 three times after that age, and his career average fell by fifteen points. It is very unusual for a slugger to see his batting average rise late in his career, as happened with Bonds and McGwire.
As Bill James put it, anabolic steroids keep a player young, physically; what they basically do is put a player with old player’s skills in a young player’s body. How many of us have wished we knew then what we know now? Basically, steroids have allowed players to have that chance.