1
...that the other guy doesn't get is worth about 0.1 runs.
Catchers receive about ten about teen thousand pitches in a 130 game season. Something like half of those pitches are swung at. Of the pitches not swung at, about half are in the strike zone. So if you get 6% of those pitches in the zone called strikes that other guys do not...that's about 180-200 extra strikes...1.8 to 2 wins. And yes...there are catchers adding a couple of wins for their receiving skill in the game...some estimates have guys like Stewart (NYY, 2013) and Russell Martin and the guy in Milwaukee (drawing a blank on his name) worth 2 wins or even a bit more for just receiving.