Stats for The Arm — Pitcher Evaluation
The stats DMP uses to evaluate pitchers, and why traditional stats like ERA and pitcher wins mislead
You should read this if:
You bet MLB props and want to understand the mental models that drive outcomes.
The Core Insight
"FIP isolates what pitchers control (strikeouts, walks, home runs). ERA is contaminated by defense, luck, and scorer judgment. The difference between them is one of the most exploitable signals in sports betting."
The MLB Mental Model
FIP (use) vs ERA (misleading)
FIP = (13*HR + 3*BB - 2*K) / IP + constant
Predicts: True pitching talent. Excellent: 3.20, Great: 3.50, Average: 4.20, Awful: 5.00
K% (use) vs K/9 (less useful)
K per batter faced, not per inning. Stabilizes in ~70 BF.
Predicts: Strikeout probability. Excellent: 27%, Great: 24%, Average: 20%, Awful: 13%
xFIP (normalizes HR luck)
Replaces actual HR/FB with league-average rate
Predicts: Whether a pitcher's HR rate is sustainable or will regress
Never use: W-L or Saves
Pitcher wins measure run support. Saves measure role, not quality.
Predicts: Nothing about pitching skill — these are team and role stats
Framework in Action: FIP vs ERA: Rick Porcello
Porcello posted 4.92 ERA in 2014, then won the Cy Young with 3.15 ERA in 2016. Same pitcher. The difference? His team defensive efficiency went from .672 to .707. FIP would have told you he was the same pitcher both years. ERA fooled everyone.
When to Apply This Framework
- ✓Every pitcher evaluation — always start with FIP, not ERA
- ✓FIP-ERA gap > 0.5 = strong regression signal for ER props
- ✓K% is reliable from early April — use it for K props immediately
When to Pass
- ⚠️Never use ERA alone to evaluate a pitcher for props
- ⚠️Never use pitcher W-L record for any analysis
- ⚠️Never trust early-season ERA without checking FIP
Key Takeaways
- ✓FIP is to ERA what true shooting is to field goal percentage — it strips out what the player does not control
- ✓K% and BB% are the most stable year-to-year pitcher skills
- ✓The FIP-ERA gap is one of the most reliably predictive signals in all of sports
How DMP Helps
DMP shows FIP alongside ERA everywhere, highlights the gap, and uses FIP as the primary pitcher skill input.