The Red Sox have a slight edge because their defense and offense are stronger overall. The Mariners have the advantage in starting pitching, which keeps the matchup close.
Why 51%?
8 of 15 categories could be scored from the data on file. The 7 unscored categories are listed openly rather than guessed at, and their weight is shared across the categories that could be measured.
Offense
The home club has a clear edge in offense (92 vs 100 wRC+).
- Team wRC+ (away) 92 MLB Stats API
- Team wRC+ (home) 100 MLB Stats API
- Team OPS (away) .690 MLB Stats API
- Team OPS (home) .717 MLB Stats API
- Runs per game (away) 4.06 MLB Stats API
- Runs per game (home) 4.27 MLB Stats API
- Hard-hit % (away) Unavailable MLB Stats API
- Hard-hit % (home) Unavailable MLB Stats API
Starting Pitcher
The away club has a strong edge in starting pitching (3.24 vs 7.46 FIP).
- Starter FIP (away) 3.24 MLB Stats API
- Starter FIP (home) 7.46 MLB Stats API
- K-BB% (away) 19.2 MLB Stats API
- K-BB% (home) 5.3 MLB Stats API
- WHIP (away) 1.10 MLB Stats API
- WHIP (home) 1.89 MLB Stats API
- Opponent OPS (away) .647 MLB Stats API
- Opponent OPS (home) 1.026 MLB Stats API
Bullpen
Bullpen splits have not been imported for both clubs.
Lineup / Platoon
The home club has a clear edge in platoon matchups (.711 vs .733 OPS in their stronger split). Starter handedness and confirmed lineups are not wired up, so this is a club-level split rather than a true lineup-versus-starter read.
- OPS vs LHP (away) .648 MLB Stats API
- OPS vs RHP (away) .711 MLB Stats API
- OPS vs LHP (home) .733 MLB Stats API
- OPS vs RHP (home) .711 MLB Stats API
- Confirmed lineup Unavailable
- Platoon advantage count Unavailable
- WAR missing from lineup Unavailable
Pitch-Type Matchup
Pitch usage and hitter results by pitch type are not in the daily snapshot yet, so this category is not scored.
Defense
The home club has a strong edge in defense (.701 vs .708 defensive efficiency). DRS and UZR have no free public source and are left out rather than estimated.
- Defensive efficiency (away) .701 MLB Stats API
- Defensive efficiency (home) .708 MLB Stats API
- Outs Above Average (away) -51 MLB Stats API
- Outs Above Average (home) 20 MLB Stats API
- Defensive Runs Saved Unavailable
- UZR Unavailable
Baserunning
Needs full player-level import for both clubs; only teams with individual hitter snapshots roll up to a team baserunning total.
Recent Form
The home club has a clear edge in recent form (4-6 vs 5-5 over ten games). Ten games is a small sample, which is why this is weighted lightly.
- Last 10 (away) 4-6 MLB Stats API
- Last 10 (home) 5-5 MLB Stats API
- Last 5 run differential (away) Unavailable MLB Stats API
- Last 5 run differential (home) Unavailable MLB Stats API
- Streak (away) L2 MLB Stats API
- Streak (home) W2 MLB Stats API
Ballpark Fit
Fenway Park suppresses home runs (95 home run factor). Neither club has a meaningful edge in how this park suits them (.150 vs .150 ISO).
- Run park factor 104 MLB park-factor baseline (multi-year estimate)
- Home run park factor 95 MLB park-factor baseline (multi-year estimate)
- Double park factor 117 MLB park-factor baseline (multi-year estimate)
- Team ISO (away) .150 MLB Stats API
- Team ISO (home) .150 MLB Stats API
Weather
No weather feed is wired up, so temperature, wind and carry are not scored.
Rest / Fatigue
Travel, days rest and schedule density are not tracked yet.
Injuries
There is no injured-list feed, so missing WAR is not scored.
Historical Calibration
This season's results back up the rest of the model, so almost no correction is needed. That read is backtested over 52 completed games at 56% accuracy.
- Backtest sample size 52 games NumSOX backtest
- Backtest accuracy 55.8% NumSOX backtest
- Brier score 0.254 NumSOX backtest
- Calibration adjustment 0 pts to the Red Sox NumSOX backtest
Regression Risk
Neither starter's ERA is far out of line with his fielding-independent numbers.
- Starter ERA (away) 4.01 MLB Stats API
- Starter FIP (away) 3.24 MLB Stats API
- Starter ERA (home) 10.80 MLB Stats API
- Starter FIP (home) 7.46 MLB Stats API
- Team BABIP (away) Unavailable MLB Stats API
- Team BABIP (home) Unavailable MLB Stats API
Live Game State
The game has not started, so score, inning and base state carry no weight yet.
Data Sources & Freshness
Each supporting statistic above carries its source and latest available update date. Missing feeds are marked unavailable and do not receive model weight.
Estimate generated Sep 26, 2026 4:40 PM.
This is a custom NumSOX estimate based on baseball statistics, not a betting line or a prediction of certainty.
- Starting Pitcher (3.24 FIP)
- Offense (92 wRC+)
- Lineup / Platoon (.711 OPS)
- Defense (.701)
- Recent Form (4-6)
- Regression Risk (+0.77 ERA-FIP)
- Offense (100 wRC+)
- Lineup / Platoon (.733 OPS)
- Defense (.708)
- Recent Form (5-5)
- Regression Risk (+3.34 ERA-FIP)
- Starting Pitcher (7.46 FIP)