A study which shows that as a catcher moves from rookie status to spending years with the same team, the pitching staff ERA improves dramatically.

INTRODUCTION

A catcher’s main job, everyone knows, is to call a game and handle the pitching staff. Everyone may know this, but in a game that has statistics for virtually everything, there seems to be precious little time and energy devoted to measuring how well catchers do their main job. Rather, we see catchers’ defense measured by how many base stealers they throw out, and all of their other defensive skills (“framing” the pitch, setting up the hitter, bringing along the pitcher) are defined anecdotally by TV and radio announcers. This study is an attempt to determine if catchers’ defensive abilities as a whole improve as they mature and adjust to a pitching staff, and to quantify this as much as is possible.

            We start by asking the question “what general factors might affect a catcher’s ability to handle a pitching staff?”. I suggest that his ability might vary with:

1)                  His age and experience

2)                  His familiarity with the pitchers he is catching

3)                  His familiarity with the batters his pitcher is facing

There may be other specific factors like special tutoring under a specific coach, but these kinds of things will not help us answer the question in general. Tests could be set up to measure any one of these. My focus in this study was to see if catchers’ defense improved in the whole, as they became familiar with a pitching staff. At the end of this paper, I will look at how the findings here might be dissected into the individual factors.

THE STUDY

            How do we best measure a catcher’s defensive abilities? I propose the only reasonable answer is the ERA of the team for which he is catching. How could we best isolate the catchers’ defensive ability from all of the other factors that cause a team ERA to rise or fall? I attempted to do this by using all of the teams that had the same primary catcher in consecutive seasons. I defined “primary” as having caught at least 85 games during a season. I used the years 1946-1987; beginning after the players returned from WWII, and going through the last year in my Baseball Encyclopedia. No adjustments were made for strike years or change in length of the season. I did not use years when a team changed cities (Brooklyn to L.A.).

There were 104 catchers used in the study. The total number of catcher years was 539, representing about 60,000 total games caught. This gave me a large set of matched pairs of teams in consecutive years using the same catcher. I found the team ERA for each year, and compared it to the league average. I also recorded the number of games the team’s catcher had caught in his career prior to the start of the season. Obviously there was always some movement of pitchers between years, some hurlers improving or declining, changes in the team defense at other positions, and changes in ballpark dimensions. But if I could get a large enough sample that all of these other factors got washed out in the noise, I would be able to see if the number of games caught by the catcher was an important contributor to the team ERA.

            As an example, I will use Bob Boone’s career. He caught at least 85 games every year except the strike year of 1981.

Table 1. Bob Boone's Career

            In Boone’s rookie year, having only caught 14 games prior to 1973, the team ERA was .33 runs per game higher than the league average. In his second season, this improved slightly to .30 higher than the league average; just .03 runs per game better. Continued improvement was shown in the next two years, after which there was a meandering slow drop off until he retired. We have 7 pairs of years while he was with the Phillies (73-73, 74-75…. 79-80), and 5 pairs of years with the Angels. Even if he had caught full time in 1981, the pair of years 80-81 would not be used in the study because he switched teams (and pitching staffs).

ORGANIZING THE DATA

            I built two groups of data. In the first, I grouped the year-pairs in bins of hundreds of career games caught: 0-99, 100-199, etc. I only used those pairs of consecutive years where the catcher’s games crossed from one grouping to the next. Thus, we can use Boone’s 73-74, but not 77-78, because he crossed right through the 500’s. This grouping was used to focus on changes from one year to the next, so I could build a function over time. Controlling the number of games caught (by 100’s) allowed me to use that as the variable that could link one group to the next. There were 306 matched year-pairs using this method. I think this method gives a good deal of organization to the data (it’s easy to use and see the trends), but I did lose a few of the samples.

Secondly, I compared rookies to veterans directly by comparing years that were somewhat further apart. In the next grouping, I again organized the data into bins of hundreds, but this time I compared them not to the previous year, but to their record 3 years ago, having caught for the same team for 4 consecutive years. I did not control how many career games the catcher had 3 seasons prior. Going back to the Boone example, between 1973 and 1976 the Phillies’ ERA improved relative to the league by .73 runs per game (from .33 to -.40). So, I recorded one data point for a catcher with career games caught in the 300s, a team ERA of -.73 compared to 3 years ago. This second grouping contained fewer points, because not as many catchers started at least 85 games for the same team for this length of time. I chose 3 years as the comparison point because

a)      the more years apart, the less data there are, so using a longer time span would be difficult, and

b)      the results of the first data grouping suggested that a 3-year span would show noticeable differences.

After trying this 3-year comparison, I wound up focusing exclusively on comparing raw rookies to veterans, since this is where the most obvious differences appeared.

COMPARING CONSECUTIVE SEASONS (GROUPING ONE)

            I found 49 consecutive year-pairs where the catcher’s career games caught went from between 0-99 to between 100-199. The average team had an ERA of .07 runs per game lower when the catchers had the extra year (= 100 games) of experience. Table 2 shows the data from every bin. As the amount of data became small for catchers with over 1000 games, I combined the last groups to ensure my sample sizes were at least 15.

Table 2

            The data in Table 2 strongly suggest that the defensive ability of the catchers improves steadily until they have caught somewhere between 400 and 800 games with the same club. The team ERA drops about three tenths of a run per game from the time they have their first full season until they reach this level of maturity. After this there is a slow rise in the team ERA until the catcher retires.

Chart 1. Cumulative ERA Differences by Catcher Experience

COMPARISONS OVER 3 YEARS (Grouping Two)

Table 3 shows the catcher year-pairs organized by bins of hundreds in a different manner. The 279-300s row shows that there were 14 catchers we could use to compare the team ERA between the year when they had between 279-399 games caught under their belts, to the team ERA 3 years prior to that. The average number of games caught in each career 3 years prior is shown. The first row indicates that after 3 years, the team ERA averaged .28 runs per game lower. It also shows that of the 14 teams represented, that 12 of the 14 had a lower team ERA (relative to the league average) when the catcher was a veteran of 279-399 games, as compared to 3 years prior when he had only caught an average of 27 games in his career.

Table 3

    * 279 was the minimum number of career games caught for any catcher who also was a starting catcher 3 years ago.

            The data in Table 3 is pretty much in agreement with that in Table 2; significant improvement in team ERA the first few years, and a slow decrease in performance toward the catcher’s later years. The item that jumped right out at me was the first 2 rows of the right hand column. Out of 38 teams, 32 of them had ERAs that were lower with the catchers who had an extra 3 years of experience. With all of the changes that likely occurred in the team pitching staffs and other defensive changes over the years, this strikes me as remarkable that about 85% of the teams would improve their pitching.

            As I studied the 38 catcher seasons involved in the first 2 rows, I noticed that the trend was even stronger when using just the catchers who had virtually no previous major league experience. So, I organized the data one last time, using ONLY the catchers who had VERY little experience (fewer than 50 games) prior to their first full-time year, and making comparison to their “prime” years. Table 2 shows that the catchers’ prime seemed to be when he had previously caught between 400 and 799 games (this is where the cumulative ERA was the lowest). I found all catchers who        

a)                  caught at least 85 games in a season, having had 50 or fewer career games coming into that year,  AND  

b)                  caught at least 85 games in other seasons, with the same team, having between 400 and 799 career games caught before these other seasons.

There were 16 comparisons. The teams, “rookie” years, and catchers used were: