Sunday, January 31, 2010

How Did Mark McGwire Age Compared To Previous Sluggers?

In some ways it looks like he aged significantly better, but I don't the evidence is completely conclusive. I took all the guys who had 400+ HRs before McGwire and found their SLG relative (RELSLG) to the league average when they were under 31 and from ages of 31-37. The I found the ratio of their old RELSLG (ORATE) to their young RELSLG (YRATE). The data was from the Lee Sinins Complete Baseball Encyclopedia. I ranked them, including McGwire. This is shown in the table below:

From age 31-37, McGwire had a 0.683 SLG while the league average was 0.435. Since .683/.435 = 1.57, his RELSLG is 157 (everything gets multiplied by 100). Under 31, his SLG was .507 while the league average was .397. Since .507/.397 = 1.28, his RELSLG was 128. Then I divided the older RELSLG by the younger. For McGwire it was 157/128 = 1.23.

He is well ahead of everyone else. If it were not for Stargell, McGwire would really stick out. One thing that occurred to me was that in moving out of Oakland and to St. Louis, he no longer had to play in a tough HR park. So for all of these hitters I then used their neutralized SLGs from Baseball Reference. They are adjusted for both the league average and park effects. The new ratios are shown below. McGwire is still first.

Mark McGwire 1.17 (actually 1.27, I made a mistake in the calculation)
Willie Stargell 1.12
Mike Schmidt 1.04
Hank Aaron 1.02
Babe Ruth 1.02
Willie Mays 1.01
Darrell Evans 1.01
Andre Dawson 1.00
Willie McCovey 1.00
Billy Williams 0.99
Dave Winfield 0.99
Harmon Killebrew 0.98
Lou Gehrig 0.98
Ted Williams 0.97
Stan Musial 0.97
Frank Robinson 0.96
Eddie Mathews 0.95
Dave Kingman 0.91
Mel Ott 0.89
Reggie Jackson 0.89
Mickey Mantle 0.89
Duke Snider 0.89
Carl Yastrzemski 0.88
Eddie Murray 0.88
Jimmie Foxx 0.86
Ernie Banks 0.84

Again, the only guy who prevents McGwire from really standing out is Stargell. If I take out McGwire, the mean is 0.9576 and the standard deviation is 0.0766. That makes McGwire 3.21 SDs' above the mean in terms of his ability to either maintain or improve his SLG as he aged. If I also took out Stargell, the mean and SD were 0.9508 and 0.0584, respectively. That makes Stargell 2.89 SDs above average. If I keep Stargell out and put McGwire back in, the mean and SD are 0.9596 & 0.0716. That would make Stargell 2.24 SDs above the mean.

I also took all of these guys and found the average age for each of the four best seasons in their neutralized SLGs with 300+ PAs. Here is how they rank from highest to lowest.

Evans 35
McGwire 33.25
Aaron 32.5
Williams 30.75
Stargell 30.5
Dawson 30.25
Kingman 30.25
B. Williams 29.75
Winfield 29.75
McCovey 29.5
Killebrew 29.25
Schmidt 29.25
Jackson 29
Musial 29
Mays 28.5
Ruth 28.5
Robinson 28
Foxx 27.5
Gehrig 27.5
Snider 27.5
Yastrzemski 27.5
Mantle 27
Murray 26.75
Banks 26.25
Ott 24.25
Mathews 23.25

Evans' top 4 ages were 26, 36, 38 and 40. McGwire's best were 34, 36, 31 and 32. He was the only guy to have all 4 at 31 or older.


SkeptiSys said...

Good read, thanks. A few comments to add to your thinking:
1) McGwire is the only player on the list that had significant injuries as a young player, which gives him a different curve than the others (healthiest seasons at older age).
2) McGwire is only one from his era on the list. Perhaps a control list of players from his era (Gwynn, Ripkin, etc) would determine if the era or McGwire is the outlier. Perhaps look at others with early injuries that never reached 400 HRs (Molitor is all I can think of now)
3)Leaving aside steroids, McGwire's training regiment was far superior to others before him, like Ruth and Mantle. This also skews his curve. Brian Downing and others could be good basis for comparison.

Cyril Morong said...

Thanks for dropping by and commenting. You make good points.

My idea of a control was to compare him to other sluggers. If we start using players who were contemporary, they might have used steroids, too. I admit this is not perfect. But I think either way there is some kind of bias.

And you're right that he did have more injuries than others. I hope that any bias from this is minimized since I am using a rate stat. But if he was playing hurt that might not help. But we don't know if some of the earlier guys played hurt sometimes, too.

Yes, he trained hard. My guess is that if we had some stat on how hard guys trained, then he would be near the top. I think Ruth may have trained harder than we normally think, especially after 1925. Ruth was still a top hitter at age 37. Mantle played his last game before he turned 37. I think Aaron and Williams trained hard. I really wish I had a variable like that to put in there.

I did do a study once and found that a greater % of players today are over 35 than ever before. That is definitely due to better training but maybe also better sports medicine and maybe PEDs.

Anonymous said...

i guess the fact that he was juicing heavily has no impact b/c you can't prove it does. uggh. sabersheep.

Anonymous said...

I would love it if you would throw in the contemporaries as a way to see who was using steroids. I also think you need to do some aggregation by eras. It seems like some of the 70's guys were trending higher...might indicate better training or earlier use of steroids than previously thought.

Anonymous said...

It would be interesting to see if better slugging percentage with age correlates with improved pitch selection (walk rate or pitches per AB). My recollection is that with McGwire his slugging percentage began to take off at the same time he became a more selective hitter. It would be interesting to see if the data supports this recollection and if so, whether its true for any of the other sluggers on your list.

Cyril Morong said...

Exactly what would be the criteria for judging who took steroids? Anyone who did better from 31-37? This gets hard to do. Not saying it can't be done, just hard. By looking at just McGwire and his predecessors, I was trying to keep it simple and I think the big improvement he had raises the question of how he did it. I admit it is possible that he was the first to really benefit from sports medicine. But then it would have to mean that sports medicine made some big leap during his career.

I avoided contemporaries because alot of them might have used steroids and again, I was just trying to contrast McGwire with his predecessors.

It can get time consuming to break everyone into eras. Not too bad with just 26 guys. But if I do a larger study, then it takes time to check exactly which years a guy played. Might be worth doing, but I won't get to that right away.

I did do a study once where the evidence indicated that players in general were aging better over time. Look in my links to my BTB articles on my home page.

Cyril Morong said...

How might we go back and measure pitch selection? I would have to do it for everyone. But thanks for the suggestion.

Cyril Morong said...

A correction: McGwire's neutralized SLG from 31-37 was 1.27 times his younger neutralized SLG, not 1.17.

Trevor Oseen said...

Good read.

Cyril Morong said...


Thanks for dropping by. Glad you liked it.


rakeback said...

I think its very selfish and transparent why McGwire finally came forward and admitted his steroid use. Does any really believe his claims that steroids didnt improve his performance?

Cyril Morong said...

Thanks for dropping by and commenting. But I am not trying to pass judgement on McGwire or anyone else. All I think I can do is examine the evidence.