Comparing players between historical eras part two: pitchersby Dan Lependorf
March 29, 2012
In my last article, I introduced a method of comparing batters from different historical eras to each other, by attempting to measure how dominant they were in the time period they played in. Here's the pitcher counterpart.
To recap, rather than using the usual "plus" stat (like OPS+ or ERA+) approach, I tried using a normalized standard deviation-based method, the z-score. "Plus" stats use simple percentage points, which work fairly well, but if the distribution of talent changes over the years, players from certain time periods will get an unjustified boost or an unfair punishment. In the deadball era of the 1910s, hitting performance fell, coupled with a decrease in the spread of talent. Not only did hitters perform worse, they also fell closer together in talent to each other. OPS+ will adjust for the deadball environment as a whole, but it won't adjust for the change in the talent spread.
For pitchers, I took every qualified player from 1871 to 2011 and calculated each year's league average and standard deviation for FIP. Graphed over time, it mirrors the changes in wOBA fairly closely. Click to enlarge.
And here's the top ten pitcher seasons by z-score.
- Pedro, Pedro, Pedro. By basically any metric, Pedro Martinez's 1999 season ranks as one of the greatest full seasons by any pitcher in baseball history, but this really helps put it in perspective. His z-score is the greatest out of any qualified pitcher, and it's not close.
- Interestingly, Cy Young doesn't appear on the list until rank 88, with his 1905 season. He's exactly the kind of pitcher who gets a little boost with normal "plus" stats as I mentioned before. He was at his best in the middle of the deadball era, when the spread in batting talent fell to its lowest level in baseball history. The change in batting performance is coupled with a change in pitching performance, as not only did pitchers get better in the deadball era, they exhibited a wider spread of performance. Cy Young's best seasons came when pitchers were more spread out, so his raw numbers indicate that he dominated the deadball era more than he actually did.
- The top 10 is a lot more varied than the top 10 batters list (Bonds, Ruth, Bonds, Ruth, you get the idea). No pitcher appears on the top ten more than three times (Martinez), and no one appears on the top 20 more than four times (Randy Johnson).
- With a FIP of 5.21 in 1960, Mudcat Grant holds the worst z-score for a qualified pitcher, at a staggering 3.48 standard deviations below the average. The worst semi-recent season would be Matt Keough in 1982, with a FIP of 5.88.
- The last 20 game loser was Mike Maroth of the Detroit Tigers, who went 9-21. He actually doesn't fare too badly by the z-score method, sitting only 1.67 standard deviations below the average.
- Like with the batters, I've provided a sortable leaderboard in the References and Resources section. Play around with it however you wish, and feel free to use it for anything you'd like.
References and Resources
Leaderboard here. Like last time, click over to list view if you want to sort it through Google Docs, or you can just download it and play with it in Excel or any other spreadsheet software. All data from Fangraphs.
Dan can be contacted here (email) or here (twitter). He welcomes all comments, even offers for cheap male enhancement pills and winnings from lotteries he didn't realize he had entered. (He really wishes you wouldn't, though.)