Earned Run Average (ERA) is, of course, the standard measuring stick of pitcher effectiveness, based on the inescapable logic that the pitcher’s ONLY job is to prevent runs from scoring (while the more elemental Runs Allowed Average would presumably be the metric that most closely correlates to run prevention, in the interests of being “fair” to pitchers and not judging them based, in part, on the errors made by their defense, I will defer to convention and concede that ERA is THE “go to” measurement).
But, how does a pitcher compile a low ERA? Firstly, of course, by limiting the runners who reach base and, then, limiting the baserunners who score. This post will break down those two attributes of pitcher skill and look at the pitchers of the past 5 decades plus who have been most proficient in each.