bayesRatings

Diamondbacks at Red Sox

MLB · Tuesday, Aug 18 · 6:10 PM CT · Fenway Park · Final ARI 4 – BOS 9
← MLB / Aug 18

Final Box Score

from the game summary
Team123456789THE
ARI004000000471
BOS302012109131
Team box
ARI·BOS
7
hits
13
1
home runs
2
3
walks
6
6
strikeouts
3
166
pitches thrown
141
1
errors
1
Top hitters
PlayerTeamH-ABRHRRBI
Gabriel MorenoARI1-3114
Adley RutschmanBOS2-4113
Mickey GasperBOS2-2112
Willson ContrerasBOS2-4101
Andruw MonasterioBOS2-4001
Nick SogardBOS2-3200
Pitchers
PitcherTeamIPHERBBK
Merrill Kelly (L)ARI4.07642
Ranger Suarez (W)BOS5.14423

For context, not in our forecast.

Game Flow

score margin
BOS +5
ARI +5
123456789
largest lead: BOS 5 · ARI 1lead changes: 2

For context, not in our forecast.

Final · our forecast was ARI 45%, BOS 55% · Updated Aug 18

Expected margin
BOS by 0.6
Expected score
BOS 4.5 – 3.9 ARI
Expected total
8.4
DiamondbacksThe matchupRed Sox
+122Our fair odds−122
3.9Expected runs4.5
+0.05Power rating+0.18
4.5Runs / game4.5
4.4Allowed / game3.8
8.2Hits / game8.3
0.98Home runs / game1.01
3.3Walks drawn / game3.2
66−60Season record67−58
5−5Last 103−7

Prediction markets

Kalshi · Polymarket US · ProphetX · Novig
ARI chance · BOS chance
Our model fair45.1%54.9%
Kalshi40.7%63.6%
Polymarket USno two-sided price
ProphetXno two-sided price
Novigno two-sided price
Full price table
TeamOur modelfairKalshipre-game · 6:10 PM CTPolymarket US ProphetX Novig 
Moneyline
ARIArizona Diamondbacks+12245%+14640.7%———
BOSBoston Red Sox−12255%−17563.6%———
SpreadBOS by 0.6
ARIArizona Diamondbacks+0.6our margin————
BOSBoston Red Sox−0.6our margin————
Totalwe expect 8.4
Over8.4our total————
Under8.4our 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

Boston Red Sox by 0.6 expected
Arizona Diamondbacks by 13 runs: <1%Arizona Diamondbacks by 12 runs: <1%Arizona Diamondbacks by 11 runs: <1%Arizona Diamondbacks by 10 runs: <1%Arizona Diamondbacks by 9 runs: 1%Arizona Diamondbacks by 8 runs: 1%Arizona Diamondbacks by 7 runs: 2%Arizona Diamondbacks by 6 runs: 2%Arizona Diamondbacks by 5 runs: 3%Arizona Diamondbacks by 4 runs: 5%Arizona Diamondbacks by 3 runs: 6%Arizona Diamondbacks by 2 runs: 9%Arizona Diamondbacks by 1 run: 15%Boston Red Sox by 1 run: 14%Boston Red Sox by 2 runs: 11%Boston Red Sox by 3 runs: 8%Boston Red Sox by 4 runs: 6%Boston Red Sox by 5 runs: 5%Boston Red Sox by 6 runs: 3%Boston Red Sox by 7 runs: 2%Boston Red Sox by 8 runs: 2%Boston Red Sox by 9 runs: 1%Boston Red Sox by 10 runs: 1%Boston Red Sox by 11 runs: 1%Boston Red Sox by 12 runs: <1%Boston Red Sox by 13 runs: <1%
← ARI wins byBOS wins by →
Boston Red Sox wins by 2 or more41%
Boston Red Sox wins by 3 or more30%
Arizona Diamondbacks wins by 2 or more30%
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

8.4 expected
1 runs: 2%2 runs: 2%3 runs: 7%4 runs: 5%5 runs: 11%6 runs: 8%7 runs: 12%8 runs: 8%9 runs: 10%10 runs: 6%11 runs: 7%12 runs: 4%13 runs: 5%14 runs: 3%15 runs: 3%16 runs: 2%17 runs: 1%18 runs: 1%19 runs: 1%20 runs: <1%21 runs: <1%22 runs: <1%
Total runs, both teams
Total over 6.565%
Total over 8.545%
Total over 10.528%
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
ARIMerrill Kelly SP · last 3 starts: 15.2 IP, 6.89 ERA, 11 Kstarted
BOSRanger Suarez SP · last 3 starts: 12.2 IP, 4.97 ERA, 7 Kstarted

Starting pitchers are part of our forecast.

Rest and Schedule

before this game
ARI·BOS
Aug 17 at BOS
last game
Aug 17 vs ARI
0 days
days of rest
0 days
6
games in last 7 days
7
5th straight road game
home / road
2nd straight home game

For context, not in our forecast.

Team Comparison

2026 season · box-score averages from 125+ games
ARI·BOS
+0.05
rating (0 = average)
+0.18
4.5
runs / game
4.5
4.4
runs allowed / game
3.8
66−60
season record
67−58
36−27
home record
30−31
30−33
away record
37−27
L2
streak
W1
5−5
last 10
3−7
8.2
hits / game
8.3
0.98
home runs / game
1.01
3.3
walks drawn / game
3.2
7.3
batter strikeouts / game
8.2
6.8
pitcher strikeouts / game
8.5
0.37
errors / game
0.49

Rating Trend

ARI · BOS · 143 days
Arizona DiamondbacksBoston Red Sox
Rating (0 = average team)

Head to Head

last 10 meetings · BOS 4−6
Aug 17at BOSBOS 11 − 1
Sep 7, 2025at ARIBOS 7 − 4
Sep 6, 2025at ARIARI 5 − 1
Sep 5, 2025at ARIARI 10 − 5
Aug 25, 2024at BOSARI 7 − 5
Aug 24, 2024at BOSARI 4 − 1
Aug 23, 2024at BOSARI 12 − 2
May 28, 2023at ARIARI 4 − 2
May 27, 2023at ARIBOS 2 − 1
May 26, 2023at ARIBOS 7 − 2

ARI · Last 10

5−5 · streak L2
Aug 17at BOS1 − 11L
Aug 16at ATL3 − 5L
Aug 15at ATL10 − 3W
Aug 14at ATL2 − 0W
Aug 12vs COL4 − 6L
Aug 11vs COL2 − 3L
Aug 10vs COL9 − 0W
Aug 9vs LAD4 − 2W
Aug 8vs LAD1 − 2L
Aug 7vs LAD4 − 3W

BOS · Last 10

3−7 · streak W1
Aug 17vs ARI11 − 1W
Aug 16at PIT3 − 8L
Aug 15at PIT4 − 0W
Aug 14at PIT4 − 8L
Aug 13at TOR7 − 0W
Aug 12at TOR4 − 6L
Aug 11at TOR3 − 5L
Aug 10at TOR1 − 2L
Aug 9vs ATH3 − 4L
Aug 8vs ATH3 − 7L