SABERMETRICS PRIMER FOR COACHES: wOBA, FIP & RUN-VALUE MODELING
Document Code: DOC-12-SABER-PRIMER
Author: ProActa Analytics Lab
1. Moving Beyond Deceptive Traditional Statistics
- Why Batting Average ($BA$) Fails: Treats a 420-foot home run the same as a 60-foot bloop single, and gives zero credit to a 10-pitch base on balls ($BB$).
- Why Pitcher ERA Misleads: Conflates pitcher quality with team defensive range, bad field conditions, and scorer biases.
2. Linear Weights & Weighted On-Base Average (wOBA)
wOBA assigns precise mathematical run values to every plate appearance outcome based on actual historical run expectancy:
$\text{wOBA} = \dfrac{0.69(uBB) + 0.72(HBP) + 0.89(1B) + 1.27(2B) + 1.62(3B) + 2.10(HR)}{AB + BB - IBB + SF + HBP}$
Evaluation Benchmark:
- $.400+$ — Elite MVP caliber
- $.340 - .370$ — Above average / high production
- $.315 - .320$ — League average
- $<.290$ — Below replacement level
3. Defense-Independent Pitching: Fielding Independent Pitching (FIP)
FIP measures only the outcomes a pitcher directly controls: Strikeouts ($K$), Unintentional Walks ($BB$), Hit By Pitches ($HBP$), and Home Runs ($HR$):
$\text{FIP} = \dfrac{13(HR) + 3(BB + HBP) - 2(K)}{IP} + \text{FIP Constant (typically 3.10 - 3.20)}$
- Rule of Thumb: If a pitcher's $\text{ERA} = 4.80$ but their $\text{FIP} = 3.10$, their defense is failing them and positive regression (fewer runs allowed) is mathematically imminent.