Another way to compare defensive positions is to look at players who played multiple defensive positions and compare their fielding records across positions. This is done in a separate article
As a general rule, pitchers tend to perform better – lower ERA, more strikeouts, better context-neutral
winning percentage – as relief pitchers than as starters. This can be measured in two ways.
First, one can compare the average winning percentage for starting pitchers and relief pitchers. Over the time period for which I have estimated Player won-lost records, starting pitchers compiled an average winning percentage of
0.499, while relief pitchers amassed a
0.501 winning percentage. From this, one could conclude that the positional average for starting pitchers is about
0.001 lower than for relief pitchers.
Such a conclusion would assume, however, that an average starting pitcher is equal in value to an average relief pitcher (on a per-inning basis). This may not be a reasonable assumption. In general, starting pitchers tend to be better pitchers than relief pitchers, particularly than non-closers.
Alternately, one can look at individual pitchers who both started and relieved in the same season. Over the seasons for which I constructed Player won-lost records, a total of
13,474 player-seasons included both starting pitching and relief pitching. Weighting each of these players’ performances by the harmonic mean
of their starting and relief pitching Player Decisions, these pitchers compiled a weighted average winning percentage of
0.476 as starting pitchers and
0.496 as relief pitchers. Using the Matchup Formula
to re-center these winning percentages around 0.500, the average winning percentage for these pitchers as starters was
0.493 and for these pitchers as relievers was
0.517. Looked at in this way, the positional average for starting pitchers appears to be about
0.024 lower than for relief pitchers.
For my work, I use this latter difference. That is, the positional average for starting pitchers is set about
0.024 lower than the positional average for relief pitchers. Because this gap is wider than the observed gap in the cumulative winning percentage for all starting pitchers vis-à-vis all relief pitchers, the result of this is that starting pitchers are, on average, slightly above-average pitchers, while relief pitchers are, on average, slightly below-average pitchers. I believe that this fairly represents the reality of how pitchers are used in Major-League Baseball.
Positional Averages for Individual Players
Unique positional averages by position
are calculated by season. A positional average winning percentage is then constructed for each individual player based on the positions at which the player accumulated his wins and losses. This is done as follows.
1. Offensive Player Decisions
For offensive player games (wins plus losses), the positional average is the average (DH-adjusted) offensive winning percentage for that position for that season. For games played under NL rules, then, a “pitcher hitting penalty” is added to the positional average. This is equal to the difference in the average winning percentage of non-pitcher position players (i.e., excluding pinch hitters, pinch runners, and designated hitters) in NL games versus the average winning percentage of these players in AL games. As the table above shows, the “pitcher hitting penalty” has been just over
1% on average. The specific penalty used in this calculation is uniquely calculated each year.
For players who accumulated offensive player decisions while playing multiple defensive positions (where, for lack of a better term, I include “pinch hitter”, “pinch runner”, and “designated hitter” as unique “defensive positions”) or who played some games under AL rules and some games under NL rules (so that the “pitcher hitting penalty” is only applied to some of his player decisions), the overall offensive positional average is simply equal to the weighted average of the unique positional averages across positions and across leagues, weighted by the number of player decisions accumulated by position and league.
2. Pitching Player Decisions
For pitchers, unique positional averages are calculated for starting pitchers and relief pitchers. These averages are calculated by year (with both leagues combined, with no DH-adjustments since an average pitcher is a 0.500 pitcher in both leagues by definition) by looking at pitchers who started and relieved in the same season (for the same team) and comparing average winning percentages of these pitchers as starters and as relievers. These average winning percentages are adjusted to an average 0.500 winning percentage using the Matchup Formula
. As noted above, on average, the Positional Average for starting pitchers is around
0.493, while for relievers the Positional Average for relief pitchers is around
0.517. These averages vary, however, by year.
3. Fielding Player Decisions
By construction, cumulative fielding winning percentage will be 0.500 for every defensive position in every league every year. Hence, the Positional Average for fielding player decisions is 0.500 for all players.
Overall Positional Average
The overall Positional Average for a player is then simply a weighted average of his offensive, pitching, and fielding averages where the weights used are the relative offensive, pitching, and fielding decisions compiled by the player.
These Positional Averages form the basis for comparing players across positions, either by comparing players to “average”
or to “replacement level”
. Positional averages by position by season are shown here
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