I will admit, I don't know why its taking so long for someone to mull through the actual pitchf/x data and break it down that way. Compare what is truly a strike, and how often a catcher is getting those called (or how often he's getting true balls to to go his pitchers' way). That would be much more convincing than this. What we have here is a very general observation and I don't put absolute confidence in the run values, but I accept the conclusions that the guys at the top of the scale are probably better than the guys at the bottom. And also, just from watching games. How many times do you see an umpire shift like he's going to raise his hand, and not? or call a late strike and the batter gets ticked off - more by the lateness of it and less by the actual call? It happens every game, it probably happens more than we even realize. Data like this just tells us there's a pattern to it. These things aren't totally random. And, really, over the course of 1440 innings, we're talking about less than a run per game separating the absolute best from the absolute worst. Its not like other defense, where you might, on a good day, field 4 or 5 balls. Although even there, you have something like 40 runs separating the absolute best from the worst. And to consider, catchers field 150+ balls every single game. I think its very plausible that they would have a greater impact. edit:words