FantasyPros has put together a glossary of sabermetrics statistics for readers to reference. Deeper statistical analysis is being used by fantasy players more and more in daily and season-long leagues. We’re providing the glossary so that you can easily reference what the stats we use in our articles refer to and how they should be used for fantasy baseball purposes. Below we’ll take a look at FIP and xFIP.

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Fielding Independent Pitching (FIP) is meant to measure how well a pitcher is pitching, based solely on what he can control. Thus, it is useful to understand how well a pitcher is pitching outside of the defense his team fields behind him. The stats used to capture this are a pitchers walks, strikeouts, home runs, hit batsman, and intentional walks. Excluded stats include wins, losses, innings, runs, earned runs, hits allowed, sacrifice hits, and sacrifice flies. The excluded stats are regressed to league average, thus putting each pitcher on equal footing. As originally conceived by Voros McCracken, the stat is helpful because there is little variance between pitchers in their ability to prevent hits once balls are put in play (to see his full articulation of pitching independent defense, follow this link).

Expected Fielding Independent Pitching (xFIP) uses the same theory as FIP but replaces a pitcher’s actual home run total with an estimated home run total that the pitcher should have surrendered based on the number of fly balls they had surrendered. The purpose behind doing this is to stabilize an inherently unstable number that is the HR/FB ratio. There are no league or park adjustments in the calculation of xFIP.

Finally, FIP and xFIP are both scaled to mirror ERA, meaning that a FIP and xFIP that is 2.50 means the same thing as an ERA of 2.50, or simply put that the pitcher is performing very well.

FIP and xFIP are good statistics to use when looking for over- or under-valued pitchers. For example, if a pitcher with a solid track record has a rough start to the season, it could inflate his 5×5 stats, including ERA and WHIP. However, by examining FIP you may see that the pitcher has been a victim of poor luck, indicating he is likely to bounce back and revert to previous numbers. Comparing the difference of ERA and FIP, for better or worse, is a great place to start when trying to find buy-low or sell-high candidates for fantasy baseball purposes.

Daniel Marcus is a correspondent at FantasyPros. To read more from Daniel, check out his archive or follow him @danmarcus3.