Catching Up -- The Hardball Times
Here is the article I remember reading several years ago.
The notion, statistically, of Catcher's ERA, or CERA, "not being statistically significant" doesn't hold water.
What this article DOES indicate, is that those individuals that are clearly superior defensive catchers absolutely do affect the total runs allowed by a pitching staff over the course of a year.
Yadier Molina, allowing all of 12 sb's at this point of the year is pretty damned impressed, as there are teams that have allowed close to 70.
So, how much is pitch calling, and how much are fewer SB, WP and PB's? Hard to say.