This article shows the relative performance of the pitching staffs of MLB teams in the first half of the 2018 season. Five of the most interesting results (details are in the chart below) are:
- The NL has 11 teams in the top 15
- Overall, the Astros have the best pitching staff; the Royals rank 30th
- The Astros have the best group of starting pitchers and the Orioles the worst
- The D-back relievers rank first and the Royal relievers rank last
- The overall top 15 teams average a higher ranking of relievers than starters . The opposite is true for the bottom 15 pitching staffs
Comparing pitching performances of individual players and teams has several challenges including:
- different numbers of batters faced by each pitcher
- roles as a starter or reliever
- excluding fielding, running and batting performance from pitching performance
- the park effect that must be eliminated to obtain fair comparisions
- adding individual performances to get team performances
These challenges have been met as described in the following paragraphs.
The results are based on the RunPlusMinus methodology for measuring the on-field performance of players and teams. The RPM statistic is a measure of each player’s performance relative to an average player’s performance. It is calculated for each of the four components — batting, running, pitching and fielding. Details of the logic involved can be found here. For purposes of this article, it suffices to know that for each batter faced, the pitcher gets a small plus or minus RPM value that takes into account the number of outs and the men on base. The RPM formula involves Expected Runs which is a widely accepted measure of the potential or threat of a given game situation.
The five challenges listed above are met as follows:
- Number of batters faced. At any point in the season the total number of batters faced by starters and relievers is very similar. The chart results show average RPMs per 100 batters faced simply to show numeric values with reasonable magnitudes.
- Starters/Relievers. The total performance for each team is broken down into starters and relievers. Approximately 60% of batters face starting pitchers and 40% face relievers. These fractions are similar for all teams and reflect the fact that starters last an average of 5+ innings.
- Pitching performance only. Although pitchers do bat, run and field the RPM values used in the analysis exclude those events.
- Park Effect is important. Pitchers who perform in batter-friendly parks such as Coors Field (Park Factor 1.411) are at a disadvantage relative to those pitching in pitcher-friendly parks such as the Oakland Coliseum (Park Factor .735). See the article “Park Effect: Measurement and Impact on Team and Player Performance” for details on run RunPlusMinus uses park effects when measuring player and team performance.
- Adding player performances to get team performances. RPMs are additive. For instance, a player’s performance for a game is the sum of his RPM values in every play in which he participated. Likewise, team pitching performance is the sum of the players’ pitching performances. Each team’s average performance is the sum of its players RPM values divided by the total number of batters faced.
To provide a relative performance of each team, the values of the “Avg +/-” values in the three columns (Overall, Starters, Relievers) are the differences between the team averages and the overall league-wide averages. This allows team performances to be ranked 1 to 30. Of course, the overall values are weighted by the number of batters faced for starters and relievers.
The chart below shows the results for each team. As stated above, the sum of each “+/-” column is zero. The “Rank” columns show rankings of the 3 “Avg +/-” columns of values.
- Measuring the quality of team pitching is a challenging task.
- The RPM statistic in RunPlusMinus provides a easy-to-use tool that accomplishes this purpose.
- Because baseball is a zero sum game, (Yogi Berra said “Good pitching beats good hitting and vice-versa”), we know that pitching performance is only half the story when assessing overall team performance.
Along with our weekly performance reports we will be publishing a report that shows the pitching performances of individual players.
Questions and comments about this report should be directed to email@example.com. Suggestions for further articles are welcome.