MLB 14 Model Factors
KBO 10 factors (FIP · xFIP · wOBA · Bullpen FIP · Recent Form · WAR · H2H · Park Factor · Elo · Defense SFR) + Statcast 4 (xwOBA · Barrel% · xwOBA-against · wOBA σ) = 14 factors.
Weight total = 100% (including home bonus 10%). Weights defined in packages/kbo-data/src/factors/mlb-base.ts. Model will update after n=150 forward cohort milestone.
Weight Summary Table
| Factor | Category | Weight | |
|---|---|---|---|
| SP FIP | Starting | 12% | |
| SP xFIP | Starting | 3% | |
| Lineup wOBA | Lineup | 10% | |
| Bullpen FIP | Bullpen | 10% | |
| Recent Form | Form | 10% | |
| Team WAR | Record | 8% | |
| H2H | Record | 3% | |
| PF | Park | 4% | |
| Elo | Rating | 10% | |
| Defense SFR | Defense | 5% | |
| Lineup xwOBA | Statcast | 5% | |
| Barrel% | Statcast | 3% | |
| SP xwOBA-a | Statcast | 4% | |
| wOBA σ | Statcast | 3% | |
| Home Elo Bonus (+24 Elo (~ +3.4%)) | 10% | ||
| Total | 100% | ||
KBO 10 Factors (Equivalent)
The 10 factors from KBO model v1.8 mapped directly to the MLB domain. Only the data sources change — statsapi.mlb / FanGraphs MLB instead of KBO sources.
1. SP FIP (Fielding Independent Pitching)
12%Category: Starting · range 1.50 ~ 6.00
ERA estimated from strikeouts, walks, and home runs only — removes fielder influence to measure true pitcher skill. Lower is better.
Why it matters: Starting pitcher matchup is the single biggest influence on a game — ranks #2 in 14-factor model weights.
Source: FanGraphs MLB · KBO Fancy Stats
2. SP xFIP
3%Category: Starting · range 1.50 ~ 6.00
FIP with home run component normalized to league-average HR/FB ratio. Removes HR luck to measure true contact suppression.
Why it matters: Eliminates HR noise from FIP → more meaningful in small samples. Supplementary layer to FIP.
Source: FanGraphs MLB · KBO Fancy Stats
3. Lineup wOBA (Weighted On-Base Average)
10%Category: Lineup · range 0.250 ~ 0.420
Weighted average of run values for BB / HBP / 1B / 2B / 3B / HR. More accurate measure of offensive production than OBP.
Why it matters: Lineup production = scoring capacity per game. Tied with SP FIP for top weight in the model.
Source: FanGraphs MLB · KBO Fancy Stats
4. Bullpen FIP (Aggregate)
10%Category: Bullpen · range 2.50 ~ 6.00
Weighted average FIP for the team bullpen (all pitchers outside the starter). High leverage in later innings.
Why it matters: Bullpen takes over after 5–6 innings — decisive in close games. High leverage factor.
Source: FanGraphs MLB · KBO Fancy Stats
5. Recent Form (Last 10 Games)
10%Category: Form · range -3 ~ +3
Difference between last-10 win rate and season win rate. ±0 = season baseline, +0.3 = strong hot streak.
Why it matters: Captures player condition, bullpen fatigue, lineup hot zones, and other daily variables. Fade-or-follow signal.
Source: statsapi.mlb.com (boxscore aggregate)
6. WAR (Wins Above Replacement)
8%Category: Record · range -2 ~ +12 (per player)
Wins a player contributes above a replacement-level player. Team lineup WAR sum = total season talent.
Why it matters: Long-term talent base. While recent form is short-term, WAR is the long-term layer.
Source: FanGraphs MLB · KBO Fancy Stats
7. Head-to-Head (H2H)
3%Category: Record · range 0.00 ~ 1.00
Win rate in direct matchups between the two teams this season. Captures matchup quirks (ballpark / rivalry / specific pitcher vs lineup).
Why it matters: Small sample (~13–19 games per season) but preserves matchup-specific patterns. Weight capped at 3%.
Source: statsapi.mlb.com (schedule aggregate)
8. Park Factor (PF)
4%Category: Park · range 85 ~ 115
Run environment at the home ballpark (hitter-friendly vs pitcher-friendly). Coors Field ~115 / Petco ~95. 100 = neutral.
Why it matters: Home ballpark adaptation = one axis of home advantage. Supplements wOBA / FIP ballpark adjustments.
Source: FanGraphs MLB · ESPN Park Factor
9. Elo Rating
10%Category: Rating · range 1300 ~ 1700
Baseball adaptation of chess Elo — updates both team ratings after each game. Stabilizes after the second half of the season.
Why it matters: Expresses team strength in a single metric. Information value Δ=+0.30 — highest among all factors (KBO backtest).
Source: KBO Fancy Stats Elo · MLB FiveThirtyEight Elo (legacy)
10. Defense SFR (Skill-Free Runs)
5%Category: Defense · range -30 ~ +30 (team)
Runs saved by defense. Positive = runs prevented above average; negative = runs allowed above average.
Why it matters: Defense component missing from FIP — SFR fills that gap. Noisy in small samples.
Source: FanGraphs MLB Def · KBO Fancy Stats SFR
Statcast 4 Factors (MLB-exclusive layer)
Batted-ball measurement layer available from the MLB Statcast Era (2015~) — 4 factors not present in the KBO model. Detailed team measurements = /en/mlb/players.
11. Lineup xwOBA (Expected wOBA)
5%Category: Statcast · range 0.250 ~ 0.420
Expected wOBA from launch angle + exit velocity. Removes luck (defense / ballpark / weather) to measure true contact quality.
Why it matters: Eliminates result noise from wOBA → more meaningful in small samples. Top Statcast weight in the 14-factor model.
Source: Baseball Savant (Statcast Era 2015~)
12. Barrel %
3%Category: Statcast · range 0% ~ 25%
Barrel = minimum launch angle + exit velocity threshold = avg .500+ AVG / 1.500+ SLG expected. Percentage per plate appearance.
Why it matters: Hard contact frequency = raw signal for home run + extra-base production capacity.
Source: Baseball Savant (Barrel definition 2015 Tom Tango)
13. SP xwOBA-against
4%Category: Statcast · range 0.250 ~ 0.420
xwOBA of batted balls allowed by the starting pitcher. Lower = better contact suppression. Complements FIP.
Why it matters: Batted ball quality layer beyond FIP's K/BB/HR. Key pitcher-side Statcast factor.
Source: Baseball Savant (Statcast pitching)
14. wOBA Standard Deviation (variance)
3%Category: Statcast · range 0.020 ~ 0.080
Standard deviation of wOBA across lineup batters. Low = balanced lineup; high = stars-and-scrubs.
Why it matters: Measures lineup depth. Same average wOBA but different σ leads to different run distributions.
Source: FanGraphs MLB · KBO Fancy Stats
Home Advantage Bonus
Home Advantage (Elo Bonus)
10%range +24 Elo (~ +3.4%)
Elo bonus of 24 points added to the home team = ~+3.4% win probability (Elo 400-point conversion). Covers ballpark familiarity, travel fatigue differential, and crowd factor.
Why it matters: Quantifies home field advantage. Applied consistently to every game.
Source: FiveThirtyEight Elo (MLB) · KBO own measurement +1.5%