CERA Thought Experiment

(1) Everybody will agree that a AA catcher -- okay, a high school catcher -- will run a lousy CERA compared to Johnny Bench (or Jorge Posada).

Pitch-calling skills, and results, go up-and-down the spectrum from Little League through Pony through High School through rookie ball through three levels of A ball, through the high minors... take 1,000 catchers and line them up. 

We all believe that.  We're starting with a given, here.

Different catchers know different things about hitters' strengths and weaknesses.  Some guys know you have to pitch Paul Konerko in.  Some don't.  Some catchers are ignorant of the fact that Brad Wilkerson cannot make contact with pitches above his hands.  Some aren't.


(2) OK, I believe that catchers in organized baseball are better and worse.  But if I believe CERA does not exist at all in the major leagues, then I've got to believe what?

That the 60 catchers in the majors all have the same pitch-calling (-framing) skills.  And how could they all be at exactly the same level?

There's a Socratic yes-into-forced-yes here.


(3) I've got to believe all 60 major league catchers are the same because ... they are 60 balloons that have bumped up against an imaginary glass-ceiling of pitch-calling together.  

If CERA skill varies up and down the ladder from HS to AAA, then how are the ML catchers all the same?  Only by all being perfect, or near-perfect.   They're not going to all stop rising together at 88% of perfect.

This means that every starting and reserve catcher in the major leagues is calling pitches 99.8% as well as they can ever be called -- now, or 1,000 years from now.

The only way in the world that 60 ML catchers could have the same real CERA is if they've all maxed out together.


(4) Have they?  In my judgment, it would be completely naive, to believe that.

We just discovered this year, that Felix' two-seam fastball moves in a way that is crushed by LH hitters.  One catcher couldn't work around that while another ignored it?

There is no room for improvement in pitch-calling here?  To believe that, I've got to believe that the things that Jorge Posada knows, about Russell Branyan, simply don't matter.   That a AAA rookie can call pitches to Branyan -- and to everybody else -- as well as a catcher who has faced him 50 times.


It is true that every ML catcher is absolutely excellent at what he does. They all have access to scouting reports.  They've all gone through a rigorous selection.

It is also true that Yuniesky Betancourt is absolutely excellent at what he does.   But the differences, between the #1 best players, and the #30 best players, show up in bases gained and lost.


Dr D


Anonymous's picture

Obviously not all MLB catchers are created equal in throwing out runners, blocking balls in the dirt, etc.  These, and CERA can be measured, counted.  Other things like knowledge, perception, and confidence are a lot fuzzier.  Is your pitcher confident enough in his catcher to throw a ball in the dirt with runners on, and on any count?  Where is the stat column for that?


While you can't look at CERA and infer too much from it about game-calling skill in any given season (because the samples are too small, and too biased), what the annual spread in CERA tells you is that the catcher himself is a significant factor in pitching (just as the home plate umpire is, as I've shown rather graphically with my attribution matrix).  When, year after year, your CERAs range +/- 1 or 1.5 runs above league average...that means the catchers are doing SOMEthing...even if we have not yet quantified exactly how much they're doing individually.
The problem with CERA is that it's not Strength-of-Pitcher and Strength-of-Opponent adjusted.  If someone bothered to calculate a CERA that accounted for which pitches Rob Johnson caught (and how many pitches from them he caught) and which hitters Rob Johnson was trying to get out (and how many times for each)...you would find a much more accurate evaluation.  And I'm fairly certain he'd still be rated as one of the best pitch-calling catchers in baseball.


And we need to understand that there are some phenomena in baseball that are so complex that we'll never be able to isolate the variables on them.
There are simply too many moving parts for us to confidently measure and find out whether it was Roger Clemens' size that allowed him to throw 250* innings a year with no problems.  You can't control for things like his arm angle, the inverted W, the acceleration of his IP load, the mounds he threw off of with the footing, and literally >100 other things.
I suspect that catcher impact on ERA is just too buried in other variables to ever isolate it.
This is part of the reason that it's so unfortunate for the BP author to have the belief, "If I can't measure it, in practical terms that's the same thing as it not existing.  If I can't measure it, it doesn't matter."
Very harmful worldview.

Anonymous's picture

Maybe it was the roids, oh yeah, size.


Are you saying that just because there is a large variation from year to year that there must be something meaningful going on? I don't think that follows at all.


I'm saying that because there is a large spread between worst and best catcher ERA within each individual season...there must be something meaningful going on.

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