The Best Pitchers Since 1920

To determine the best pitchers we could look who had the lowest ERAs. But we might want to adjust those for the time period and park effects. In some years it might be easier to have a low ERA than other years. In 1968 the AL ERA was 2.98. In 1996 it was 5.00. The same can be said for parks. From 2002-04, 36% more runs were scored at Coors Field in Denver than the average NL park while 16% fewer were scored at Dodger Stadium. We might also take into account innings pitched since a pitcher can have a low ERA but if he pitches infrequently. One more factor is the role of fielders. Pitchers who have great fielders behind them will allow fewer hits and therefore have lower ERAs. I used all of these factors in this analysis.

Last week I wrote an article called "The Best Fielding Independent Pitching Seasons From 1920-2005." There I explain the methods I used to incorporate the factors that I mentioned above. The data I used includes all pitching seasons with 150+ IP (so any data from a pitcher's season with under 150 IP did not figure in-this means I'm pretty much only looking at starting pitchers). Pitchers were compared to the league averages in strikeouts, walks and HRs allowed using how many standard deviations above or below the mean each pitcher was. Once all of those factors were taken into account, each pitcher was placed in the context of a league with approximately a 3.70 ERA.

Here are the lowest 25 ERAs with a minimum of 1,500 IP:

For a minimum of 3,000 IP the lowest 25 are:

As I mentioned above, a low ERA is great but might not be valuable if a guy's IP are low. So I predicted how many wins each pitcher would get based on their predictd ERA assuming their team scored an average number of runs. For this I used what Bill James calls the "Pythagorean Formula." It says that winning percentage can be approximated by runs scored squared divided by runs scored squared plus runs allowed squared. Each pitcher's number of games was found by dividing their IP by 9. Then the pitcher's games won was predicted by multiplying the Pythagorean percentantage times the number of games.  Subtracted from that was the number of games an average pitcher would have won (.5 times games) to get games won above average.

For example, Roger Clemens had 4,332.67 IP. That works out to 481.4 games. He had a predicted ERA of 2.45. If his team scored 3.696 runs per game the Pythagorean .695. That would give him 334.46 wins while the average pitcher would have had 240.7. So Clemens was 93.76 wins above average. Here are the top 25 in wins abvove average.

I also looked at wins above replacement level, assuming that a replacement level pitcher would have a .400 winning percentage (I think Dvd Avins may have been the first researcher to look at pitchers' value this way). Looking at Clemens again, in 481.4 games, the replacement level pitcher would win 192.56 games (481.4*.400). Clemens' 334.6 is about 142 wins above that. So here are the top 25:

I also tried a .333 pct for the replacement level pitcher. Here are the top 25:

Sources:

The Sean Lahman Database

X
Log In Sign Up

forgot?
Log In Sign Up

Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior users will need to choose a permanent username, along with a new password.

Your username will be used to login to SB Nation going forward.

I already have a Vox Media account!

Verify Vox Media account

Please login to your Vox Media account. This account will be linked to your previously existing Eater account.

Please choose a new SB Nation username and password

As part of the new SB Nation launch, prior MT authors will need to choose a new username and password.

Your username will be used to login to SB Nation going forward.

Forgot password?

We'll email you a reset link.

If you signed up using a 3rd party account like Facebook or Twitter, please login with it instead.

Forgot password?

Try another email?

Almost done,

By becoming a registered user, you are also agreeing to our Terms and confirming that you have read our Privacy Policy.

Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.

Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.

Spinner.vc97ec6e

Authenticating

Great!

Choose an available username to complete sign up.

In order to provide our users with a better overall experience, we ask for more information from Facebook when using it to login so that we can learn more about our audience and provide you with the best possible experience. We do not store specific user data and the sharing of it is not required to login with Facebook.

tracking_pixel_9351_tracker