As of February, 2019, users of this website are able to make their own choices of positional averages to be used in evaluating player values. A full discussion of positional averages and other aspects of player evaluation using Player won-lost records can be found in a 50-page PDF essay which I have written, Comparing Players Using Player Won-Lost Records
This article gives a brief overview of the options available for calculating positional averages for pitchers.
I believe that there are three possible ways to calculate positional averages for pitchers.
(1) Pitching is pitching: the positional average is 0.500 for all pitchers for all seasons by construction.
(2) Starting pitchers and relief pitchers should have different positional averages, which should be calculated empirically each season. That is, in 2018, the overall winning percentage for starting pitchers (excluding their offense) was 0.497; the overall winning percentage for relief pitchers (again, only on defense) was 0.504. Those are your positional averages for 2018.
(3) Starting pitchers and relief pitchers should, indeed, have different positional averages, but option (2) assumes that the pool of starting pitchers and the pool of relief pitchers are equal. What we should do, instead, is focus on pitchers who pitched as both starters and relievers. Doing this produces positional averages for 2018 of 0.487 for starting pitchers and 0.518 for relief pitchers.
In the past, I have chose option (3). In keeping with my general decision to allow users to choose positional averages, I have extended this to include allowing users to choose from among these three options for pitchers. Enter any numbers desired in the boxes associated with these three options and positional averages for pitchers will be calculated as a weighted average of the choices based on the numbers entered.
For example, entering values of 1, 2, and 3 for options (1), (2), and (3), respectively, would calculate a weighted positional average for pitchers equal to (1/6) option 1 (6 = 1 + 2 + 3), (2/6) option 2, and (3/6) option 3.
If the user does not enter anything, the default positional average weights the three options equally: (1/3) Option 1, (1/3) Option 2, and (1/3) Option 3.
All articles are written so that they pull data directly from the most recent version of the Player won-lost database. Hence, any numbers cited within these articles should automatically incorporate the most recent update to Player won-lost records. In some cases, however, the accompanying text may have been written based on previous versions of Player won-lost records. I apologize if this results in non-sensical text in any cases.
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