The league average provided here is park adjusted. Greg Maddux in 2004 would be compared to a 4.24 league average because he threw his home games in Wrigley. Jason Jennings, hurling for the Rockies, would compare to a 5.05 league average. The reason why it's done that way is to normalize the results so that what you're talking about is how well Pitcher A did instead of basing your conclusions on the circumstances in which the guy pitched. For instance, Wilson's 4.36 ERA looks a whole lot better than Jennings's 5.51 and Eric Milton's 4.75 from 2004. Yet when you normalize them for park factors, all three wind up with a 92 ERA+. A 100 is average and the better you pitch, the higher that ERA+ will climb.Originally Posted by SMcGavin
Beyond that, finishing 51st out of 86 ERA qualifiers is nothing to write home about. Yet if you rank players using a park-adjusted ERA+ (slightly different from the calculation WOY used above), Wilson would drop into the high 60s in a dead heat with the guys who finished 61st, 71st and 81st in overall ERA.