In this on-going series of posts about run scoring in Major League Baseball, for this installment I'll turn the equation around and look at runs allowed. In order to account for the changing run scoring environments, the runs allowed by individual teams is compared to the league average for that season, creating an index where 100 is the league average. In this formulation, a score below 100 is a good thing; a team with an index score of 95 allowed runs at a rate 5 percentage points below the league average.
Having written the original code in R, it's now a very simple process to change a few variable names and create the equivalent of the earlier runs scored analysis, but looking at runs allowed. This is one of the most important benefits of a code/syntax environment, an option that doesn't exist if you are using a point-and-click GUI interface.
In the original data set (the "Teams" table from the Lahman database), the variable "R" is for runs scored and "RA" is runs allowed. So throughout the code simply changing R to RA will do the trick. For example, the variable "Teams.merge$R_index_rank" is changed to "Teams.merge$RA_index_rank".
Similarly, when it comes time to write the summary tables a simple change within the file name is sufficient. (I chose to change the bit with "off" (for offense) to "def" (for defense), so "Teams.hi_off" becomes "Teams.hi_def".)
NOTE: The R code for this analysis is posted at at Github. The original code, necessary to process the file and create a data table "Teams. merge" is here, and the supplementary code to incorporate individual team runs allowed is here.
So what are the results?
The only other team with more than three appearances on the list are the Los Angeles Dodgers, who appear twice when Sandy Koufax was on the team (1965 and his final season, 1966). The 1975 Dodgers pitching staff featured the 2.29 ERA of Andy Messersmith, while in 2003 Hideo Nomo and Kevin Brown were the stars of the rotation.
One other thing that I can't help but note is that the New York Yankees only show up on the list once, in the strike-shortened 1981 season. Below, we'll take a closer look at the team history.
Now we'll move to the teams that allowed runs at a rate greater than 20 percentage points above the league average. There are more than twice as many clubs on this list -- 54 in total.
One of the factors that appears to play a role is expansion. Some of the clubs on the list were in their first or second years as a new franchise, and the poor quality pitching shows. (While this makes intuitive sense, a closer look at this phenomenon is warranted, along with a comparison of their hitting performances.)
One such team are the Colorado Rockies, whose inaugural season of 1993 makes the list. What sets the Rockies apart is that they also have six other seasons of allowing runs at a rate more than 20 percentage points higher than the league average. This in spite of only played in 20 of the 66 seasons in the analysis. At least to some degree, the well-established phenomenon of a high run-producing environment at Coors Field can explain this.
And similarly, we can look at a single team's performance over time with a few adjustments to the R code.
When looking at run production, the Seattle Mariners were one object of attention. So let's even things up by looking at their pitching since 1977. They started out, like all expansion teams, with poorer than average performance ... their worst ever year was 1978, nearly 24 percentage points above the league average rate of runs allowed. In recent years, the Mariners have had four seasons of better than average performance. Having Felix Hernandez doesn't hurt, and neither does that fact that Safeco Field tends to play as a pitcher's park.
|(click to enlarge)|
The inverse of that are the many seasons that the Yankees have had allowed far fewer runs than the league average. Coupled with the similarly dominant offensive performance identified in the earlier post, there is no wonder that the Yankees are (arguably) the most successful professional sports franchise in the world.
|(click to enlarge)|
And finally, the Braves, who we saw earlier had an unusually large number of appearances on the low number of runs allowed side of the ledger. As noted earlier, the franchise's first few years in Milwaukee (starting in 1953 and ending in 1965) were marked by strong pitching. But nothing in the team's history can match the Maddux-Glavine era -- the ten seasons from 1993 through 2002 -- where the run suppression was consistently outstanding.
|(click to enlarge)|