Boston Red Sox vs Seattle Mariners Prediction
Expert prediction, odds analysis, and best bet for Boston Red Sox vs Seattle Mariners on June 21, 2026.
Win Probability
Best Bet
Current Odds
API-Sports| Team | Moneyline | Run Line | Total | Impl. Prob. |
|---|---|---|---|---|
Boston Red SoxAway | +105 | -213 | -125 | 49% |
Seattle MarinersHome | -125 | +170 | -103 | 56% |
Additional Full-Game Markets
First 5 Innings (F5)
Statistical Analysis
- 1
Seattle Mariners project 4.0 runs: 4.2 RF/G offense vs 4.1 RA/G Boston Red Sox pitching.
- 2
Boston Red Sox project 3.9 runs: 3.9 RF/G offense vs 3.9 RA/G Seattle Mariners pitching.
- 3
Seattle Mariners season record: 39–39 (50% win rate).
- 4
Boston Red Sox season record: 39–36 (52% win rate).
- 5
Seattle Mariners home: 4.0 RF/G, 3.7 RA/G (54% home win rate).
- 6
Seattle Mariners last 5: 2.4 RF/G, 4.4 RA/G (1d rest, 5 G last 7d).
- 7
Boston Red Sox last 5: 2.8 RF/G, 4.2 RA/G (1d rest, 5 G last 7d).
- 8
Moneyline edge vs market: -4.1%.
How This Prediction Was Made
Show model inputs ▼
Team Data Inputs
| Metric | Sox | Mariners |
|---|---|---|
| Season Win% | 52.0% | 50.0% |
| Games Played | 75 | 78 |
| Season RF/G | 3.95 | 4.18 |
| Season RA/G | 4.07 | 3.94 |
| Run Diff/G | -0.12 | 0.25 |
| Last-5 RF/G | 2.80 | 2.40 |
| Last-5 RA/G | 4.20 | 4.40 |
| Venue RF/G | 4.50 | 3.97 |
| Venue RA/G | 4.08 | 3.69 |
| Venue Win% | 50.0% | 53.8% |
| Form (last-5) | 1/5 W | 2/5 W |
| Rest Days | 1 | 1 |
| Games (Last 7d) | 5 | 5 |
| Data Quality | 100% | 100% |
Run Projection Formula
Projected runs = weighted blend of offense + opponent defense (season & recent) + venue split.
| Component | Value | Wt | Contrib |
|---|---|---|---|
| Season RF/G | 3.95 | 30% | 1.184 |
| Opp Season RA/G | 3.94 | 30% | 1.181 |
| Recent RF/G (5G) | 2.80 | 15% | 0.420 |
| Opp Recent RA/G | 4.40 | 15% | 0.660 |
| Venue RF/G | 4.50 | 5% | 0.225 |
| Opp Venue RA/G | 3.69 | 5% | 0.185 |
| Projected runs | 3.9 | ||
| Component | Value | Wt | Contrib |
|---|---|---|---|
| Season RF/G | 4.18 | 30% | 1.255 |
| Opp Season RA/G | 4.07 | 30% | 1.221 |
| Recent RF/G (5G) | 2.40 | 15% | 0.360 |
| Opp Recent RA/G | 4.20 | 15% | 0.630 |
| Venue RF/G | 3.97 | 5% | 0.199 |
| Opp Venue RA/G | 4.08 | 5% | 0.204 |
| Home bonus | 0.12 | — | 0.120 |
| Projected runs | 4.0 | ||
Win Probability Blend (Home)
Three signals are blended to produce the final home win probability.
| Signal | Prob | Weight | Contribution |
|---|---|---|---|
| Run margin (projected score diff) | 51.4% | 65% | 33.41% |
| Team strength (win% + venue) | 50.0% | 25% | 12.50% |
| Recent form (last-5 W/L) | 56.0% | 10% | 5.60% |
| Final home win probability | 51% | ||
Confidence Score Breakdown
| Factor | Points |
|---|---|
| Base (win probability distance from 50%) | +51 |
| Run margin bonus (larger margin = more predictable) | +0.5 |
| Data quality adjust (more game history = tighter estimates) | +10 |
| Form agreement (recent form aligns with season record) | 0 |
| Market odds available (confirms edge vs vig) | 0 |
| Final confidence score (medium) | 61 |
Market Edge Analysis
Edge = model probability minus market-implied probability. Positive edge = model sees value vs the book.
| Bet Type | Edge | Signal |
|---|---|---|
| Moneyline | -4.1% | ✓ fade |
| Run Line (-1.5) | -5.9% | ✓ fade |
| Over/Under | +1.2% | no edge |
| Mariners Team Total | +3.7% | no edge |
| Sox Team Total | +4.1% | ✓ value |
| F5 Moneyline | +3.9% | no edge |
| F5 Over/Under | -0.0% | no edge |
4%+ edge threshold required for a value bet recommendation.
Boston Red Sox vs Seattle Mariners Prediction — Expert Analysis
Our model projects Seattle Mariners to win this matchup with a 51% win probability. The predicted final score is Sox 3.9 – Mariners 4.
Boston Red Sox come into this game with a 39-36 record, good for a 52.0% winning percentage.
Seattle Mariners are 39-39 at home this season, with a 50.0% overall win rate. Home field advantage gives them an additional 3-4% boost to their projected win probability.
Our best bet for this matchup is the Boston Red Sox Team Total Over 3.5, which carries a medium confidence rating based on current statistical inputs.