The Case Against a Case Against FIP

At FanGraphs, our headline WAR number for pitchers is based on FIP. Because of that, and because people enjoy debating and arguing, there’s a yearly refrain that you’ve probably heard. “FanGraphs pitching WAR only considers (X)% of what a pitcher does, how can that be used for value?” No one would dispute that year-one FIP does a better job of estimating year-two ERA than ERA does – or at least, not many people would – but the discussion around whether FIP does a good job of assigning year-one value is alive and well.
One reason for this view is pretty obvious. FIP considers home runs, strikeouts, walks, and hit batters to estimate pitcher production on an ERA scale. Our WAR does some fancy stuff in the background – it treats infield fly balls, which virtually never fall for hits, as strikeouts, and it adjusts for park and league. In the end, though, it’s estimating pitcher value using just three (well, actually four — HBPs always draw the short straw) outcomes. There are a lot of other outcomes in baseball!
In 2021, roughly 39% of plate appearances ended in a homer, strikeout, walk, hit batter, or infield pop up. One thing you could think, in recognition of that fact, is that FIP-based WAR doesn’t consider enough of a pitcher’s production. You wouldn’t use 40% of a hitter’s plate appearances to calculate their WAR, so why do it for pitchers? But that doesn’t actually make sense, as David Appelman pointed out to me recently. Assuming “average results on balls in play” is actually going to be pretty close for every pitcher, by definition. Read the rest of this entry »