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There’s a commonly held belief in sabermetric circles that catchers reach
their offensive peak later that players at other positions. Presumably, the
physical strain of playing catcher inhibits their development as hitters.
The emergence of Darren Daulton at age 30 is typical of this
phenomenon. However, to the best of my knowledge, there has not been a
study to back up that intuition.

I decided at look at the issue in more depth, using the free player
statistic database at http://www.baseball1.com. I did two different
studies, looking for evidence that catchers peak later than players in
general.

Study 1

For the first study, I computed the aggregate RC/27 for all catchers who
had 300+ PA at a certain age, and looked at the total performance of those
players the following year, provided that they still played catcher most
frequently and amassed 300+ PA. I then looked at the ratio between the
aggregate RC/27s, and compared it to a prior study that did the same thing
for all players.

Numbers above 1.000 indicate that the group as a whole improved the
following year, while numbers below that indicate that the group as a whole
declined the following year. I’ve included only ages that had at least 10
qualifying catchers (all but age 21 had 20+ data points).

      Catcher   AllPlayers
Age    Ratio       Ratio
21     1.057       1.112
22     0.974       1.059
23     0.977       1.031
24     1.065       1.015
25     0.988       1.024
26     0.982       0.999
27     0.988       0.985
28     0.988       0.987
29     0.970       0.983
30     1.002       0.976
31     0.912       0.970
32     0.969       0.973
33     1.014       0.970
34     0.914       0.946
35     0.886       0.947

The study does not show a clear trend that would indicate a later peak for
catchers. Very young catchers seem to wear down slightly while other
position players are improving. Catchers hold their value pretty well
during their late 20s, comparable to other positions. The 30 to 33 range is
very volatile, with ratios jumping all around, but the average for the
period is .974, comparable to the all-player average of .972, so the
decline is about as quick. After age 34, things go downhill very quickly
for catchers, a trend noticeable even in the very small sample sizes beyond
age 35 that aren’t shown here.

Study 2

For the next study, I looked at the age at which the player had his season
with the highest total contribution. Several years ago, I had previously
done a study with Adjusted Batting Runs for all players (available at
http://www.stathead.com/bbeng/woolner/peakage.htm). The Baseball1 database
did not have ABR available, so for the catchers’ portion of the study, I
used a comparable measure called Marginal Runs Created (MRC), defined as:

OUTS*(RC/Out - LgRC/Out), where RC/Out = OBP*SLG/(1-AVG)

but not adjusted for park. I looked only at players who had 10 seasons with
100+ PA and with catcher as their primary position. I computed the age they
had their highest MRC total, and took that as their peak season (players
who reached identical peak totals in two different seasons are credited
with two peak seasons). I then counted how many catchers peaked at each
age, and compared it to the results from my previous study.

           Catchers                 All Players
Age   Num   Peak%   Cumul%      Num   Peak%   Cumul%
21      1    0.8%     0.8%       29    1.8%     3.2%
22      6    4.7%     5.4%       55    3.5%     6.7%
23      5    3.9%     9.3        87    5.5%    12.2%
24      7    5.4%    14.7%       90    5.7%    17.9%
25     14   10.9%    25.6%      148    9.4%    27.2%
26     12    9.3%    34.9%      160   10.1%    37.4%
27     15   11.6%    46.5%      163   10.3%    47.7%
28     13   10.1%    56.6%      155    9.8%    57.5%
29     11    8.5%    65.1%      138    8.7%    66.2%
30     12    9.3%    74.4%      141    8.9%    75.2%
31     12    9.3%    83.7%      107    6.8%    82.0%
32      5    3.9%    87.6%       91    5.8%    87.7%
33      3    2.3%    89.9%       68    4.3%    92.0%
34      7    5.4%    95.3%       46    2.9%    94.9%
35      1    0.8%    96.1%       25    1.6%    96.5%
36      2    1.6%    97.7%       22    1.4%    97.9%
37      1    0.8%    98.4%       13    0.8%    98.7%
38      2    1.6%   100.0%        9    0.6%    99.3%

As with position players, the most frequent peak age for catchers is 27.
The peak range for catchers extends from 25 to 31, with a strong dropoff on
either side. The dropoff for all players ends a year earlier at age 30, so
there is some credence to the idea that catchers can still reach their peak
around age 30-31 more often than players who play other positions.

The "Cumul%" column measures what percentage of players have seen
their peak season by a certain age. Fewer catchers of a given age have
peaked than comparable position players at every age until age 31, though
the differences are small. Given that we are looking at an aggregate
measure of value, rather than a rate measure, a managerial bias towards
giving veteran catchers more playing time could be enough to tip the
percentages slightly towards the older catchers as we observed.

Conclusion

Catchers do not improve or maintain their rates of production into their
late 20’s or early 30’s. There’s only the slightest tendency for catchers
to have their peak season at ages 30 and 31 more often than other position
players.

Overall, I don’t view the evidence as a strong trend for a later offensive
peak. Perhaps we should abandon the idea of catchers developing more
slowly, and recognize that the physical demands of the position will tend
to reduce both the length of their peaks and the length of their careers.