How many more errors will deadball pitchers cause? I keep reading that they will cause more errors but I can't find any indication of how many errors. does Walter Johnson cause another 10 errors or another 50 errors?

1905 Honus Wagner, SS: .935
1905 SS average: .0.931
Pitcher from 1957: .9609
Batter from 1887: .871
Result: 0.928

1905 Honus Wagner, SS: .935
1905 SS average: .0.931
Pitcher from 2005: 0.97399
Batter from 1991: 0.968765
Result: 0.9615

Figure a shortstop gets 1000 chances. Wagner with the 1887 pitcher will make ~72 errors. Wagner with the 2005 pitcher will make ~39 errors. The difference is 33.

Now extrapolate that across the other positions.

now I see why people are upset. are we sure this is the formula? I would think a much smaller percantage of the difference should be applied.

well that is a very extreme example. and i think that if honus wasn't already a bad fielder it would be less extreme. but if you use 1880s hitters it seems like you'll be turning your opponents' gloves into mush. of course their gloves will be mush too...

the thing that bothers me about your example jfranco is that Wagner actually peforms worse in this update if facing a hitter from a poor fielding year even though Wagner is better than the league average during his season of use....I thought the whole purpose of normalization of fielding was to "fix" the deadball era and allow these guys to become useable....it makes no sense to me that Wagner (and others) could actually be worse depending on the matchups.....

I assume WiS doesn't apply fielding percentage evenly across every type of "chance". In other words, errors occur a lot less on popups or line drives to the shortstop than they do on grounders.

If so, you can probably cut Wagner's realistic chances in which he might make an error in the example (which is probably on the high side anyway) down by maybe 1/4 or 1/3. Meaning the expected jump in errors would decrease too.

If we are going to assume Wagner gets 1000 chances the difference would be about 1/2 of 33. In the above example we have 1000 tries with an 87 pitcher and 1000 tries with a 2005 pitcher, making the total 2000 chances. Given 500 chances with each pitcher the seasonal difference would be ~16.5

WIS posted a calculator here:

linky

I'll run through a couple quick examples

pitchers:
Walter Johnson 1913 - league fielding % for SS was .936
Greg Maddux 1995 - league fielding % for SS was .971

shortstops:
Troy Tulowitzki 2007- his F% is .987, league F% is .972
Honus Wagner 1908 - his F% is .943, league F% is .928

we'll just use a nice normal league F% at SS of .950 for the batter in all scenarios, and we'll use 1000 chances

Tulo and Walter: 18 errors, .982
Tulo and Maddux: 15 errors, .985

Previously, Tulo would have made 13 errors with either pitcher.

Honus and Walter: 50 errors, .950
Honus and Maddux: 40 errors, .960

Previously Honus would have made 57 errors with either pitcher.

The following examples give all the various combinations for a historically good fielding infielder from the dead-ball era...

1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1903: .912
Batter from 1903: .912
Result: .933
Expected number of errors (1000 Total Chances): 67

This makes sense. We want the fielder to hit his field% in a single-season progressive league.


1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 2009: 973
Batter from 1903: .912
Result: .947
Expected number of errors: 53

1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1903: .912
Batter from 2009: .973
Result: .947
Expected number of errors: 53

So, the hitter and pitcher have equal weight on the fielder.


1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from2009: .973
Batter from 2009: .973
Result: .968
Expected number of errors: 32

Putting an old-time fielder with a modern hitter and pitcher cuts his errors in half.


1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1885: .876
Batter from 1903: .912
Result: .927
Expected number of errors: 73

1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1903: .912
Batter from 1885: .876
Result: .927
Expected number of errors: 73

Putting an old-time fielder with only one 1880's pitcher or hitter isn't that much worse... only 6 errors


1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1885: 876
Batter from 1885: .876
Result: .921
Expected number of errors: 79

This is still only 13 errors worse... not that significant


1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 1885: .876
Batter from 2009: .973
Result: .938
Expected number of errors: 62

1903 Honus Wagner, ss .933
1903 SS average: .912
Pitcher from 2009: .973
Batter from 1885: .876
Result: .938
Expected number of errors: 62

Mixing a worse pitcher and better hitter (and vice versa) kind of cancels each other out and the fielder will do about the same.

Now let's look at a modern fielding shortstop who's worse than league average...

1985 Julio Franco, ss .949
1985 SS average: .964
Pitcher from 1985: ..964
Batter from 1985: .964
Result: .949
Expected number of errors: 51

1985 Julio Franco, ss .949
1985 SS average: .964
Pitcher from 1885: .876
Batter from 1985: .964
Result: .930
Expected number of errors: 71

1985 Julio Franco, ss .949
1985 SS average: .965
Pitcher from 1885:
Batter from 1885:
Result: .920
Expected number of errors: 80

Notice that given the same 1885 hitter and pitcher, Wagner (.933 irl) and Franco (.949 irl) end up with about the same normalized fielding percentage.