Fielding Dependent Pitching (FDP) is an umbrella name for a group of pitching metrics that measure those aspects of a pitcher’s contribution that are not covered by metrics like FIP (Fielding Independent Pitching), as the name indicates. Whereas FIP tries to isolate, in a simple fashion, the “three true outcomes” for which a pitcher is most clearly responsible (home runs, walks, and strikeouts), the metrics under the FDP rubric try to quantify everything else.
FDP metrics encompass and break down those aspects of traditional pitching metrics like ERA (Earned Run Average) that are deliberately ignored by DIPS metrics such as FIP. In other words, the relationship between FIP and FDP can be expressed in a simple conceptual formula: RA9-Wins (Win value based on actual runs allowed) = FIP-Wins + FDP-Wins
As noted above, FDP is not one metric; it is a group of metrics. They are grouped on FanGraphs’ player pages under the Win Values section.
RA9-Wins is just like the standard Wins Above Replacement for pitchers, except it uses runs allowed per nine innings (RA/9) as its basis rather than a modified version of FIP. This the most straightforward of the FDP stats, as it is basically a traditional pitching metric but translated into an expression of pitcher value.
BIP (balls in play) -Wins is an estimate of how many wins a pitcher has added by having a BABIP above or below league average. It adjusts for park and league. The full formula for BIP-Wins is:
((((H-HR)*(w1B * p1B + w2B * pxBH) ) / (TBF – HR – BB – HBP – SO)) – lgwBABIP) * (TBF – HR – BB – HBP – SO) / PF / RtW * -1
p1B = singles as a percentage of hits that are not home runs
pxBH = doubles and triples as a percentage of hits that are not home runs
w1B = linear weight value of a single
w2B = linear weight value of a double
RtW = runs to wins converter
PF = park factor
lgwBABIP = league average: ((H-HR)*(w1B * p1B + w2B * pxBH)) / (TBF – HR – BB – HBP – SO)
LOB (left on base) -Wins is an estimate of how many wins a pitcher has added as a result of stranding runners on base. This is just a general name for a component that involves different aspects of a pitcher’s game with respect to baserunners, for example: controlling the running game, pitching differently with runners on, or pitching out of the stretch.
FDP-Wins is the sum of BIP-Wins and LOB-Wins. It is also the difference between RA9-Wins and FanGraphs’ standard FIP-based pitching WAR. Again, remember the formula: RA9-Wins = FIP-Wins + FDP-Wins
Things to Remember:
● FIP and other DIPS metrics are generally better at predicting things in smaller samples, while in the long-run RA9 tends to be the best. However, many pitchers never even make it to the long run, and sometimes we want to get an idea of how well a pitcher is pitching while he is doing it, not three full seasons later.
● While the acronyms “FIP” and “FDP” emphasize fielding as what they are trying to isolate out, this is somewhat misleading (unintentionally). The difference between RA9 and FIP is not all about fielding. Other aspects are involved, they are simply more difficult to isolate as skills. For example, the differences between pitchers on balls in play is not just about defense. Some of it is skill. Some of it is defense. And a lot of it is probably just random variation.
● There is much we still do not know about pitching. That is true of baseball in general, but pitching is a bigger mystery than hitting. Having different win-metrics is a way of acknowledging the unknown and the possibility of different approaches.
● When evaluating knuckleball pitchers, it’s better to use RA9-Wins, as those pitchers have been shown to consistently generate weaker contact than typical pitchers.