I was thinking about this when looking hard at two pitchers with very similar records: Curt Schilling and Kevin Brown.
By some statistics, Schilling’s career and Brown’s career are freakishly similar. They pitched almost the exact same number of innings:
Schilling: 3,261 innings
Brown: 3,256 innings
They had very similar won-loss records.
Schilling: 216-146
Brown: 211-144
They have ERAs that are close, and their ERA+ —which compares them against league average and considers park factors — is identical:
Schilling: 3.46 ERA, 127 ERA+
Brown: 3.28 ERA, 127 ERA+.
And yet most people — including me — think Schilling was a noticeably better pitcher (For instance: I annually vote Schilling for the Hall of Fame, and did not vote Kevin Brown). Why? Well, there are some clear reasons. Brown was mediocre in the postseason, Schilling was legendary. Schilling had more good seasons. Schilling has the greatest strikeout-to-walk ratio in baseball history.*
...
Now, you consider the ballparks they played in, the leagues, and so on — look, Kevin Brown was a superb pitcher. But, in reality, he wasn’t as good as Schilling at preventing runs. His ERA is, at least in part, an illusion.
This is when some people will say: No! Not an illusion! You can’t blame Kevin Brown for those unearned runs.
I want to talk about this word “blame” in a minute.