FIP: judge pitchers on what they control
If defense and luck own balls in play, what's left that's purely the pitcher's?
Strikeouts, walks, and home runs. No fielder touches any of them. Fielding Independent Pitching builds a number from only those three, then scales it to look like an ERA so your intuitions transfer.
Why it forecasts better
This is BABIP's lesson (Level 2) weaponized: since pitchers barely control balls in play, an ERA built on them is noisy, while K/BB/HR skills are stable. Result: today's FIP predicts next season's ERA better than today's ERA does. When ERA and FIP disagree, the smart money follows FIP.
A 3.80 ERA / 3.10 FIP pitcher is probably better than his ERA (bad defense or luck). A 3.10 ERA / 4.20 FIP pitcher is probably riding a wave. This one comparison is the highest-value habit in pitching analysis.
The formula (optional — skippable)
FIP = (13·HR + 3·(BB+HBP) − 2·K) ÷ IP + constant(≈3.1)
The 13/3/2 are run-value-derived; the constant glues it to the ERA scale.
How this stat lies to you
- Some pitchers DO manage contact quality somewhat (soft-tossers with elite movement) — FIP shortchanges them season after season.
- HR/FB luck contaminates the HR term — xFIP's complaint, next lesson.
- It's a talent estimate, not an account of what happened — the runs on the scoreboard were real.
Check yourself
1. Which three events does FIP use?
2. Mid-season: ERA 4.60, FIP 3.20. Best bet on his rest-of-season?