Everything that has been said about walks, HBP, and errors being at more of a premium in pitchers parks is true and correct, imo. There is also a flip to this: Strikeouts. While BB/HBP/errors are baserunners that occur independent of park, Ks are outs you get independent of park. Thus, in a pitcher's park, where I've already built a good D and the park helps me on balls in play, I'm going to pay very little attention to Vel. In Coors, every out I can get that the park plays no factor in is precious, and I'm going to pay attention to Vel much more strongly. (In a neutral park I consider it a secondary factor).