What I'm asking is whether a pitcher with a high ERA over the course of a whole season or career actually allows fewer runs versus the Brewers, as that's the perception (e.g. a guy like Glendon Rusch, who always sucks, will do better against the Brewers). And what I'm trying to explain is that, if you see a pitcher in June with a 6.6 ERA, without knowing anything else about him, you'd expect the Brewers to score less than 6.6 earned runs per 9 innings against him. That's because, most likely, that pitcher's skill ERA is less than 6.6. Now, if you want to use a career ERA for a guy who's racked up 600+ innings, that's a lot better, of course. I think that right way to tackle this is to compare a pitcher's projected ERA to their performance with the Brewers. A pitcher's projection is out statistical best guess at a pitcher's true talent level, after all.