I’ve answered more than a few reader questions in the last week surrounding Craig Kimbrel‘s value as a keeper. He’s a unique relief pitchers in that he strikes out as many batters as a low-strikeout starting pitcher despite tossing about one-third the innings, and his ERA will likely be somewhere in the 1.40-1.60 range.
The value Kimbrel brings in Ks is easy to quantify — if he strikes out 30 more batters than Jonathan Papelbon, that’s worth just as much as Matt Cain striking out 30 more batters than Johnny Cueto. But what about the impact Kimbrel has in ERA? Well, that’s not quite as easy to judge on the fly.
Our player rating system (PSR) has a built-in ERA conversion component that allows us to properly value players who have different ERAs over different innings workloads. It struck me yesterday that this might make a useful table when trying to evaluate what impact a reliever’s ERA has compared to a starting pitcher who throws three times as many innings. It can also be used when evaluating trades that involve a 200-inning starter and a 160-inning starter, or really any situation in which you need to know the exact impact/value a pitcher’s ERA has based on the amount of innings he pitches.
So here you go. Now you can say, “If Kimbrel finishes with a 1.60 ERA in 60 innings, that has the same value as a starting pitcher finishing with a 3.24 ERA over 210 innings. Awesome!”
Yes, awesome indeed.