If you enjoyed the previous diagrams for position player WAR and offensive stats, then you’ll enjoy the diagrams for pitching stats. Just like the previous two diagram posts, the best instructions on how to precisely calculate the stats are in our library. However, the diagrams provide a visual conceptual overview of what affects the different pitcher stats.

The first set of stats are divided into three subcategories, based on denominator. The first is balls in play (BIP) and the pitcher batting average on balls in play (BABIP) stat. This is the same as batter BABIP except it’s calculated from the pitcher’s perspective. Total batters faced (TBF) is the second subcategory, where there are two stats: K% and BB%. These again mirror the batter’s version.

The innings pitched (IP) is the subcategory with the most familiar pitching stats. Innings pitched effectively counts every out the pitch has made, divides that by three to get IP. The most basic stats IP-based stats are K/9, BB/9, and HR/9. Walks plus hits per inning pitched (WHIP), a stat we don’t use a lot at FanGraphs, divides the total number of hits and walks by the number of innings pitched. Earned run average (ERA) does the same thing but also scales it to a full, 9-inning game. Fielding independent pitching (FIP) and expected FIP (xFIP) both use defensive-independent outcomes to estimate ERA. The FIP constant scales the stat to be comparable to ERA. xFIP is the same as FIP except for the HR input is change to fly balls (FB) and converted to HRs by multiplying FB by the league average HR/FB ratio.

Since I was in a diagramming mood, I also made diagrams for pitcher’s win-loss (W, L) records and saves (SV). The SV diagram only has the scenarios when a SV occurs, so negative cases aren’t represented. If you follow the diagram and answer counter to what is available the pitcher does not earn a SV.