(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.

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(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.

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(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.

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(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.

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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.

Cheers,

Dr D