bayesRatings

Cubs at Mariners

MLB · Friday, Aug 21 · 9:10 PM CT · T-Mobile Park · Final CHC 5 – SEA 6

Final Box Score

from the game summary
Team12345678910THE
CHC30000001105121
SEA0400100001682
Team box
CHC·SEA
12
hits
8
4
home runs
1
2
walks
4
11
strikeouts
7
133
pitches thrown
167
1
errors
2
Top hitters
PlayerTeamH-ABRHRRBI
Alex BregmanCHC3-5223
Cal RaleighSEA1-4113
Ian HappCHC2-5111
Pete Crow-ArmstrongCHC1-4111
Brendan DonovanSEA2-5001
Carson KellyCHC2-5000
Pitchers
PitcherTeamIPHERBBK
Matthew BoydCHC6.06423
Ryan Zeferjahn (L)CHC0.21010
Emerson HancockSEA5.28306
Seranthony Dominguez (W)SEA1.00001

For context, not in our forecast.

Game Flow

score margin
SEA +3
CHC +3
12345678910
largest lead: SEA 2 · CHC 3lead changes: 1

For context, not in our forecast.

Final · our forecast was CHC 55%, SEA 45% · Updated Aug 21

Expected margin
CHC by 1.0
Expected score
CHC 4.6 – 3.6 SEA
Expected total
8.2
CubsThe matchupMariners
−124Our fair odds+124
4.6Expected runs3.6
+0.23Power rating−0.05
5.1Runs / game3.9
4.3Allowed / game4.3
8.5Hits / game7.6
1.28Home runs / game1.13
4.2Walks drawn / game3.3
74−54Season record60−68
6−4Last 104−6

Prediction markets

Kalshi · Polymarket US · ProphetX · Novig
CHC chance · SEA chance
Our model fair55.4%44.6%
Kalshi51.7%52.7%
Polymarket USno two-sided price
ProphetXno two-sided price
Novigno two-sided price
Full price table
TeamOur modelfairKalshipre-game · 9:10 PM CTPolymarket US ProphetX Novig 
Moneyline
CHCChicago Cubs−12455%−10751.8%———
SEASeattle Mariners+12445%−11252.7%———
SpreadCHC by 1.0
CHCChicago Cubs−1our margin————
SEASeattle Mariners+1our margin————
Totalwe expect 8.2
Over8.2our total————
Under8.2our total————

These are each venue’s last prices before the start (Kalshi’s moneyline: its pre-game close). Odds are the price to buy that side now, taker fee included; the small percent is the implied chance of that same price. Highlighted is the best price in the row among venues on the same line. — means not listed (hover or tap for why). A market price is not the true chance of winning.

Margin range

Chicago Cubs by 1.0 expected
Chicago Cubs by 14 runs: <1%Chicago Cubs by 13 runs: <1%Chicago Cubs by 12 runs: <1%Chicago Cubs by 11 runs: 1%Chicago Cubs by 10 runs: 1%Chicago Cubs by 9 runs: 1%Chicago Cubs by 8 runs: 2%Chicago Cubs by 7 runs: 3%Chicago Cubs by 6 runs: 4%Chicago Cubs by 5 runs: 5%Chicago Cubs by 4 runs: 7%Chicago Cubs by 3 runs: 8%Chicago Cubs by 2 runs: 11%Chicago Cubs by 1 run: 12%Seattle Mariners by 1 run: 17%Seattle Mariners by 2 runs: 9%Seattle Mariners by 3 runs: 6%Seattle Mariners by 4 runs: 4%Seattle Mariners by 5 runs: 3%Seattle Mariners by 6 runs: 2%Seattle Mariners by 7 runs: 1%Seattle Mariners by 8 runs: 1%Seattle Mariners by 9 runs: <1%Seattle Mariners by 10 runs: <1%Seattle Mariners by 11 runs: <1%Seattle Mariners by 12 runs: <1%Seattle Mariners by 13 runs: <1%Seattle Mariners by 14 runs: <1%
← CHC wins bySEA wins by →
Chicago Cubs wins by 2 or more45%
Chicago Cubs wins by 3 or more34%
Seattle Mariners wins by 2 or more26%
Decided by one run29%

Centered on the expected margin above; shape from each team's expected runs, with ties after nine settled as one-run games, matched to 14,698 past MLB games.

Total range

8.2 expected
1 runs: 2%2 runs: 2%3 runs: 8%4 runs: 6%5 runs: 12%6 runs: 8%7 runs: 12%8 runs: 8%9 runs: 10%10 runs: 6%11 runs: 7%12 runs: 4%13 runs: 4%14 runs: 3%15 runs: 2%16 runs: 1%17 runs: 1%18 runs: 1%19 runs: 1%20 runs: <1%21 runs: <1%22 runs: <1%
Total runs, both teams
Total over 6.563%
Total over 8.543%
Total over 10.526%
Total from 7 to 1037%

Centered on the expected total above; shape from each team's expected runs, with ties after nine settled as one-run games, matched to 14,698 past MLB games.

Starting Pitchers

from the box score
CHCMatthew Boyd SP · last 3 starts: 19.0 IP, 6.16 ERA, 8 Kstarted
SEAEmerson Hancock SP · last 3 starts: 17.2 IP, 3.57 ERA, 17 Kstarted

Starting pitchers are part of our forecast.

Rest and Schedule

before this game
CHC·SEA
Aug 19 vs CHW
last game
Aug 20 at MIL
1 day
days of rest
0 days
6
games in last 7 days
6
road after a home game
home / road
home after a road game

For context, not in our forecast.

Team Comparison

2026 season · box-score averages from 128+ games
CHC·SEA
+0.23
rating (0 = average)
−0.05
5.1
runs / game
3.9
4.3
runs allowed / game
4.3
74−54
season record
60−68
38−27
home record
33−29
36−27
away record
27−39
L1
streak
L1
6−4
last 10
4−6
8.5
hits / game
7.6
1.28
home runs / game
1.13
4.2
walks drawn / game
3.3
8.6
batter strikeouts / game
8.6
7.7
pitcher strikeouts / game
8.5
0.37
errors / game
0.52

Rating Trend

CHC · SEA · 146 days
Chicago CubsSeattle Mariners
Rating (0 = average team)

Head to Head

last 9 meetings · SEA 4−5
Jun 22, 2025at CHCSEA 14 − 6
Jun 21, 2025at CHCCHC 10 − 7
Jun 20, 2025at CHCSEA 9 − 4
Apr 14, 2024at SEACHC 3 − 2
Apr 13, 2024at SEACHC 4 − 1
Apr 12, 2024at SEASEA 4 − 2
Apr 12, 2023at CHCSEA 5 − 2
Apr 11, 2023at CHCCHC 14 − 9
Apr 10, 2023at CHCCHC 3 − 2

CHC · Last 10

6−4 · streak L1
Aug 19vs CHW0 − 3L
Aug 18vs CHW4 − 3W
Aug 17vs CHW7 − 5W
Aug 16vs STL4 − 11L
Aug 15vs STL4 − 8L
Aug 14vs STL3 − 0W
Aug 13at WSH0 − 7L
Aug 12at WSH12 − 6W
Aug 11at WSH8 − 6W
Aug 9at KC10 − 2W

SEA · Last 10

4−6 · streak L1
Aug 20at MIL4 − 7L
Aug 19at MIL7 − 5W
Aug 18at MIL0 − 22L
Aug 16at HOU3 − 2W
Aug 15at HOU10 − 5W
Aug 14at HOU7 − 10L
Aug 13at NYY1 − 0W
Aug 12at NYY5 − 10L
Aug 11at NYY1 − 4L
Aug 9vs TB1 − 4L