Part of the numbers was a comparison of how pitches were called with different catcher/pitcher combos. However, since Mauer accounted for over half the sample of the starting pitchers he caught during the period you cannot get a good comparison, especially when Butera accounted for another large chunk of those pitchers sample. Whether you call it inconsistent movement/poor command the effect is still the same, Mauer ends up having a lot of glove movement in order to catch him, which means pitches are less likely to be called strikes because the pitcher isn't hitting his spots. Samuel Deduno and Throwing Strikes | FanGraphs Baseball Also for a fastball that is a large amount of horizontal movement spread (10 inches between highest and lowest value), not to mention it has both left and right cut on it. For example looking at the most recent starts from Gibson, Pelfrey, Diamond, Verlander, and King Felix, all of them had cut in only one direction on their fastball and 4 of them had less than 5 inches of difference between the highest and lowest horizontal numbers. See Glavine, see also Maddux, see also Radke. Reputation also plays into it and while counts makes some difference on borderline strikes I doubt Deduno getting the benefit of the doubt in poor counts is anything more than a red herring given the issue here is clearly fastball command/inconsistent movement.