How many home-runs did Mark McGwire REALLY hit?

After the jump, let's take a look and at the numbers posted over the course of Mark McGwire's career, and see if we can work out how much impact steroids had on his figures.

Bob Costas: Could you have hit 70 home runs — a home-run ratio greater than anything Babe Ruth did in his time — without using steroids?
Mark McGwire: Absolutely. I was given this gift by the Man Upstairs... The only reason I took steroids was for my health purposes. I did not take steroids to get any gain for any strength purposes... There is not a pill or an injection that is going to give me the hand-eye — or give any athlete — the hand-eye coordination to hit a baseball. A pill or an injection will not hit a baseball.

Oh, dear. I watched the interview late last night, and almost felt sympathy for McGwire,. It can't have been easy for him, even if, for most of those watching the admissions can hardly have come as any kind of a shock, and were more a confirmation of what we already assumed. I do have a great degree of empathy for why he adopted the "I'm not here to talk about the past" approach at the Congressional hearings - though "I take the fifth" would have been a great deal more straightforward and honest. But where McGwire loses credibility is the above exchange. He hit 15% more home-runs in a single-season than any legitimate [see the above chart] hitter in the history of the game. That's as if someone ran 100 meters in 8.33 seconds - yet it's not in any way connected to his long-term use of steroids?

McGwire admits he first started using them "on a consistent basis [in] the winter of '93/'94," when he had just turned thirty. Tangotiger has looked into aging curves for hitter and has found that a) power hitters reach their best later than slap hitters, and b) the peak age has got a bit older of late. For power hitters born between 1960-69, which includes McGwire, he found the age to be 29.1 years, conveniently close to the age when McGwire started taking steroids. If he was at his peak then one might expect his number post 30 to mirror those up to that point - without PEDs, anyway. Let's compare the stats:

Turns out the split is just four plate-appearances off dividing McGwire's career exactly in half. But the difference in output is obvious. His batting average increased by 11%; his on-base percentage by 19%; and his slugging percentage by 32%. On that basis, McGwire is right: steroids don't give you the hand-eye co-ordination needed to hit a baseball. However, they certainly help make it go further when you do. Pre-steroids, his SLG high in any season with 200+ PAs was .618. After taking them up, his SLG low in any such year, until his final, injury-crippled season, was .628. Some of that may be going from a pitcher-friendly park in Oakland, to a neutral one in St. Louis. However, his SLG over the last three years by the bay was .674 - exactly the number posted in the second half of his career.

Whether he took steroids for the purpose is largely irrelevant: the evidence is that they - not "the Man upstairs" - massively improved his power. Pre-steroid McGwire hit a very solid 40 homers per 162 games. But post-steroid Big Mac hit 22 more per full season. And that's when he (allegedly) wasn't even trying "to get any gain for any strength purposes." Go...sorry, "the Man upstairs" alone knows what steroids might do if actually used for that purpose. But it certainly seems credible that, for a top-notch hitter, 20 balls over the course of a season that would otherwise be just loud outs, could leave the park if chemically-assisted. If his numbers had mirrored those pre-steroids, that would be 458 total HR, a drop of 125 on the number actually achieved.

For amusement, let's apply the same adjustment to Barry Bonds*. According to Game of Shadows, Bonds* started juicing "in 1998," at age 33. Comparing his SLG percentages up to and after that season, the numbers are .556 and .712. That's a 156-point difference - less than ten points off the 165-point boost experienced by McGwire. If we apply the same 20 HR/162 game PED deduction to Bonds* from 1999 on, that's 134 homers less. The sad thing is, the resulting "clean" career total of 628 homers would still have been enough to punch a ticket to Cooperstown.

What difference does this make to McGwire's Hall of Fame chances? On the plus side, he's come out and opened up, answering just about every question Costas fired at him [credit, incidentally, Costas for a good job on the interview]. On the other hand, it confirmed our worst fears: the '98 home-run chase which enthralled the nation was a sham, an illusion of fair contest. Before yesterday, I wasn't sure how I'd feel in the light of such revelations from a high-profile player. Now, I know: McGwire cheated - not once or twice, but systematically, for years. Having seen the apparent scope of the benefit gained, I'm forced to conclude he shouldn't be allowed within a hundred miles of Cooperstown.