Today, we unveiled the latest addition to our family of Simple WAR Calculators: a version for pitchers! Creating a WAR calculator for pitchers proved to be much harder than it was for position players (hence the year-long lag between the release of the first Simple WAR Calculator and now), and I thought understanding it might also be somewhat more difficult for those who are unfamiliar with wins above replacement. So here’s a quick guide to how the calculator works.
First you’ll need to provide some basic information: what kind of a pitcher the player in question is, how much you expect him to pitch, and what the average ERA is. Whether he is a starter or a reliever affects how easy he is to replace—it’s a lot harder to be a starting pitcher than it is to come out of the bullpen. The number of innings also matters (a pitcher who throws 200 frames is twice as valuable as a similarly skilled teammate who throws only 100), as does the run environment (a 4.50 ERA means something very different if the league average is 5.00 instead of 4.00).
Next, the calculator needs an estimate or projection for the pitcher’s ERA. If you’ve got one, great—skip ahead to the next part. If not, the calculator will make it for you. Just write in some predictions for strikeouts and walks and the calculator will give you a figure you can use.
Once all the inputs are filled in, the calculator calculates how many runs your pitcher saves his team compared to what a hypothetical “replacement-level” player (the kind of guy you’d claim on waivers or call up from Triple-A in an emergency) would allow given the same opportunity. Imagine that in a certain run environment a replacement-level pitcher would have a 5.50 ERA as a starter (or 4.50 as a reliever); a pitcher who throws 100 innings with a 4.00 ERA would be worth 16.7 runs above replacement (or 5.6 as a reliever).
The final step in calculating WAR is converting runs to wins. For hitters this is as easy as dividing runs above replacement by a constant converter (the ratio is usually around 10 runs per win, depending on the year and ballpark) but for pitchers this too is adjustable because they change the run environment for the opposing team. So the conversion denominator is calculated based on both the league-average ERA and your pitcher’s projected performance. This is then multiplied by the price of a win’s worth of player production on the free agent market (for 2012, FanGraphs put it at $4.5 million per win) to get the player’s monetary value.
Got all that? Then go check it out!