Baseball Player Won-Loss Records
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Starting Pitchers versus Relief Pitchers



In evaluating Player won-lost records, I consider starting pitcher and relief pitcher to be two separate positions. Some differences between starting pitchers and relief pitchers are explored here.

Pitcher Contexts
Over the entire Retrosheet Era, the overall Player won-lost records of starting pitchers and relief pitchers were as follows:

Context-Neutral Context Win Adjustments
Pitcher - Role Decisions Win Pct. Inter-Game Intra-Game Combined Inter-Game Intra-Game
Starting Pitcher 208,1850.4991.0021.0761.078-0.0020.003
Relief Pitcher 88,8580.5020.9950.8210.8170.0040.005
Non-Save Situations 56,9710.5000.4371.0180.4450.001-0.031
Save Situations* 18,4750.5112.0290.8101.644-0.0010.065
Tie Games 13,4130.4991.9400.6491.2580.007-0.045
*Save situations are defined here as situations in which the winning or tying run is either on base, at bat, or on deck. This excludes saves earned by pitching at least three innings in a win, regardless of situation, or by pitching at least one inning with a 3-run lead. This also includes what would be classified as "holds" instead of saves.

There are several comparisons that I find interesting here. The first one is that relief pitchers compiled a slightly higher overall winning percentage than starting pitchers: 0.502 to 0.499. As a general rule, pitchers tend to perform better – lower ERA, more strikeouts, better context-neutral winning percentage – as relief pitchers than as starters. In fact, however, the difference in context-neutral winning percentages actually understates the impact of this. This is because, in general, (with many exceptions, of course) starters tend to be better pitchers than relievers, especially non-closers. To some extent, many, if not most, relief pitchers are failed starters.

A better way to determine the extent to which pitching in relief would be expected to improve one’s player winning percentage, then, is to focus on pitchers who both started and relieved within the same season and compare these player’s winning percentages. Among all seasons for which I have estimated Player won-lost records (1930 – 2016), a total of 15,060 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 2.4% (0.024) lower than for relief pitchers. This difference forms the basis for calculating Positional Averages and Positional Replacement Levels.

The second comparison above is the difference in contexts. Inter-game context is comparable for relief pitchers, 0.995, and for starting pitchers, 1.002. This virtual equality masks large differences depending on situation. Relief pitchers in save situations*, 2.029, and tie games, 1.940 have an extremely high inter-game context. Relief appearances in non-save situations have an average inter-game context less than half as big as that of starting pitchers (0.437).
*As noted above, "save situations" here do not include saves earned by closers for pitching the ninth inning with a 3-run lead.

The story is quite different, however, for intra-game context. Starting pitchers have an average intra-game context of 1.076 vs. 0.821 for relief pitchers. This is because average intra-game context is highest in the early innings of games.

Combining inter-game and intra-game context, starting pitchers have a combined average context of 1.078 vs. 0.817 for relief pitchers. This difference in combined overall context is taken account of in my construction of final Context-Neutral player won-lost records through the calculation of an Expected Context.

The use of relief pitchers has changed considerably over the 60+ years over which I have estimated Player won-lost records. The same results since 2000 are shown in the next table.

Context-Neutral Context Win Adjustments
Pitcher - Role Decisions Win Pct. Inter-Game Intra-Game Combined Inter-Game Intra-Game
Starting Pitcher 53,7920.4960.9881.0931.080-0.002-0.001
Relief Pitcher 27,9150.5081.0230.8270.8450.0040.012
Non-Save Situations 17,7690.5060.4171.0340.431-0.000-0.017
Save Situations 5,9280.5182.1370.8191.751-0.0010.068
Tie Games 4,2180.5022.0100.6571.3200.006-0.050


The general relationships identified above are all still true. More recently, however, there has been a somewhat greater spread in winning percentages between starting pitchers and relief pitchers. Relief pitchers have also seen a somewhat higher average inter-game context in recent years than for earlier years.

Changes in Relief Pitcher Roles over Time
The next table shows a breakdown of context-neutral pitching decisions by pitcher role by decade from the 1950s to the 2000s (2000 - 2016).

Breakdown of Context-Neutral Pitching Decisions by Role
Pitcher-Role 1950s 1960s 1970s 1980s 1990s 2000s
Starting Pitcher 72.7%71.3%72.3%69.7%67.3%65.8%
Relief Pitcher 27.3%28.7%27.7%30.3%32.7%34.2%
Non-Save Situations 18.6%18.5%17.4%18.3%20.4%21.7%
Save Situations 4.9%5.7%5.9%7.1%7.4%7.3%
Tie Games 3.8%4.6%4.4%4.9%4.9%5.2%


From the 1950s through the 1970s, the overall percentage of (context-neutral) pitching decisions earned by relief pitchers was relatively constant. This relatively constant overall usage masked underlying changes in relief pitcher usage, however. Specifically, over this time period, the use of relief pitchers declined by 1.2% in non-save situations, but rose 1.0% in save situations.

The 1980s saw the greatest increase in overall relief pitcher decisions of any decade (2.6%). This increase in relief-pitcher usage spanned all three roles shown here, with the use of relief pitchers in non-save situations returning to 1950s - 60s levels, while the share of total pitcher decisions earned by relief pitchers in save situations and tie games increased by a combined 1.7%.

The 1990s and 2000s have seen a continuing increase in overall relief pitcher usage. Interestingly (to me), however, the increase in relief pitcher usage over the past 20 years appears to be almost entirely centered on increased relief pitcher usage in non-save situations*.
*The definition of "save situations" which I use here does not include saves earned by closers for pitching the ninth inning with a 3-run lead. I suspect the number of such saves has increased over this time period, which may be part of the apparent increase in what I am identifying as "non-save situations".

To get a better feel for how the changing roles of relief pitchers have interacted with changing usage, the final table here shows a breakdown of context-dependent pitching decisions by pitcher role by decade from the 1950s to the 2000s (2000 - 2016).

Breakdown of Context-Dependent Pitching Decisions by Role
Pitcher-Role 1950s 1960s 1970s 1980s 1990s 2000s
Starting Pitcher 79.2%77.1%77.6%74.4%72.2%71.1%
Relief Pitcher 20.8%22.9%22.4%25.6%27.8%28.9%
Non-Save Situations 8.9%8.4%7.7%8.1%9.0%9.4%
Save Situations 7.3%8.9%9.3%11.4%12.4%12.7%
Tie Games 4.6%5.6%5.4%6.1%6.3%6.8%




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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