MLB matchup analysis
Mariners vs Red Sox Prediction, Odds and Model Pick
Monday, August 31, 2026 at Fenway Park · 6:45 PM ET
LyDia prediction: Boston Red Sox moneyline
The case for Boston Red Sox
The case for Seattle Mariners
What to watch
Why the setup score is what it is
Why the price is what it is
Read the full model output
Boston Red Sox is an official moneyline pick because it clears both gates: 69.5% model win probability and 8.3/10 Lab Rating. LyDia projects 69.5% against a 51.5% no-vig market number, a 17.9% model edge at -116. Boston Red Sox owns the starting pitcher edge by 13 points. Bullpen read: Adds caution. Boston Red Sox's pen efficiency: Below average (3.4/10). Lineup check: Boston Red Sox is a touch above its season form (+0.028 OPS); Seattle Mariners is in a cold stretch (-0.061 OPS). Recent form supports this side and is included in the unified run projection.
Final result
Mariners 8, Red Sox 9
How the analysis held up
Boston Red Sox won, the side LyDia's model favored.
Payton Tolle (Boston Red Sox), the starter LyDia's pitcher score favored, actually outpitched George Kirby: 5.2 IP, 4 ER (6.35 ERA) against 5.0 IP, 5 ER (9.00 ERA). The edge held up. Neither starter actually pitched well tonight, though — this is a smaller-of-two-bads comparison, not a starter who dealt.
The Seattle Mariners bullpen was not flagged pregame, but it had a night worth noting: 3 earned runs allowed over 4.1 relief innings (6.23 ERA) — quietly worse than the pregame read implied. Note: 1 of the runs charged to the Seattle Mariners pitching staff overall was unearned — not something the bullpen's stuff should be blamed for.
The Boston Red Sox bullpen was flagged as elevated risk pregame (High risk). In relief it actually allowed 4 earned runs over 4.1 innings (8.31 ERA) — the risk read showed up.
Seattle Mariners scored 8 in a game that went 10 innings — not compared against the 2.5 pregame projection, which assumed nine.
Boston Red Sox scored 9 in a game that went 10 innings — not compared against the 5 pregame projection, which assumed nine.
Game information
| Matchup | Seattle Mariners at Boston Red Sox |
|---|---|
| Date | Monday, August 31, 2026 |
| First pitch | 6:45 PM ET |
| Venue | Fenway Park |
| Starting pitchers | George Kirby vs Payton Tolle |
| Weather | Game-time forecast: 75°F, 0% precipitation chance, 4 mph wind from S. |
Starting pitcher matchup
Full Pitcher Matchup Tool →| Metric | Mariners | Red Sox |
|---|---|---|
| Pitching plan | Traditional starter | Traditional starter |
| Expected innings | 6 | 5⅔ |
| Throws | R | L |
| LyDia pitcher score (higher is better) | 62 | 75 |
| ERA (lower is better) | 4.19 | 3.23 |
| WHIP (lower is better) | 1.35 | 1.10 |
| K/9 (higher is better) | 7.5 | 10.1 |
| K-BB% (higher is better) | 14.4% | 20.8% |
| K% (higher is better) | 20.0% | 27.7% |
| BB% (lower is better) | 5.6% | 7.0% |
| BB/9 (lower is better) | 2.1 | 2.5 |
| HR/9 (lower is better) | 1.1 | 1.0 |
| Ground-ball rate | 46.9% | 38.3% |
| Fly-ball rate | 53.1% | 61.7% |
Pitcher edge: LyDia gives Payton Tolle a 13-point edge over George Kirby, driven mainly by K/9 (10.1 vs 7.5) and K-BB% (20.8% vs 14.4%).
How to read this: the scorecards above name the starters; every number lives in this table.
Strikeout Projections Full strikeout projections →
Same data source as the Pitcher Matchup Tool, where every starter on the slate is compared side by side.
Recent form
Full Stats page →Mariners are 4-6 in their last 10 and averaging 3.4 runs per game over the last 15 days; Red Sox are 6-4 in their last 10 and averaging 4.5 runs per game over the last 15 days. On the season Red Sox carry the better run differential per game (+0.62 against -0.53).
| Metric | Mariners | Red Sox |
|---|---|---|
| Last 10 | 4-6 | 6-4 |
| Last 10 by venue (away team on the road, home team at home) | 3-7 on the road | 7-3 at home |
| OPS, last 15 days | 0.618 | 0.754 |
| wOBA, last 15 days (hot/cold read) | 0.281 | 0.334 |
| Runs per game, last 15 days | 3.4 | 4.5 |
| K% last 15 days (lower is better) | 27.3% | 17.5% |
Last 15 days only. Hot and cold streaks for all 30 teams live on the Stats page.
30-day offense
Full offense tool →| Last 30 days | Mariners | Red Sox |
|---|---|---|
| OPS | 0.659 (-0.027 vs szn) | 0.791 (+0.063 vs szn) |
| Runs per game | 3.52 (-0.417 vs szn) | 5.34 (+0.892 vs szn) |
| wOBA (model offense input) | 0.296 (-0.010 vs szn) | 0.346 (+0.024 vs szn) |
| K% (lower is better) | 24.5% (+1.2% vs szn) | 18.3% (-3.0% vs szn) |
Over the last 30 days the Red Sox have been the better offense, 0.346 wOBA to 0.296. They are running hot against their own season line (+0.024 wOBA). Mariners are striking out at 24.5% over the window — something the opposing starter can lean on.
Season profile
Full Stats page →| Metric | Mariners | Red Sox |
|---|---|---|
| Record | 64-73 | 74-63 |
| Run differential / game (team quality) | -0.53 | +0.62 |
| Runs scored / game (offense, season) | 3.90 | 4.48 |
| Runs allowed / game (defense, season, lower better) | 4.43 | 3.86 |
| Season OPS | 0.679 | 0.726 |
| K% season (lower is better) | 23.4% | 21.2% |
| OPS vs opposing hand (season) | 0.634 | 0.711 |
Season-long team quality, not recent form. Run differential and run environment come from the season standings; splits for all 30 teams live on the Stats page, including the run environment table.
The Map
Full interactive map →Every team on today's slate, on any two axes you pick. Mariners and Red Sox are highlighted.
Bullpen matchup
Full Bullpen Fatigue Index →Risk is what the model actually uses: fatigue blended with how well the pen has pitched. High fatigue with high efficiency is a tired pen that is still getting outs.
| Metric | Mariners | Red Sox |
|---|---|---|
| Fatigue | 5.3/10, Normal | 7.9/10, Tired |
| Efficiency | 5.1/10, Average | 3.4/10, Below average |
| Combined risk | 5.3/10, Normal | 8.7/10, High risk |
| Relief innings, last 7 days | 20.0 | 29.0 |
| Back-to-back arms | 3 | 5 |
| 7-day ERA | 4.05 | 6.21 |
| 7-day WHIP | 1.30 | 1.59 |
Fatigue measures workload. Efficiency measures recent run prevention. Combined risk is what the moneyline and totals systems use.
Run total projection
Full Totals Projections →The model and market are close. Team totals remain research-only until their graded sample is established.
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