Reds vs. Mariners prediction: Seattle favored to win Tuesday's MLB matchup [7/21/2026]
Get Cincinnati Reds vs Seattle Mariners predictions for MLB Tuesday.
The Seattle Mariners and Cincinnati Reds will lock horns in MLB action at T-Mobile Park on Tuesday, starting at 9:40 PM ET.
The Mariners will start Luis Castillo (3-8, 4.93 ERA), while the Reds have opted for Chase Burns (11-1, 2.54 ERA).
Based on updated simulations, Dimers' advanced MLB model gives the Mariners a slight edge with a 52.9% win probability over the Reds.
This article offers further insights into Tuesday's Reds vs. Mariners matchup, including best bets and picks.
Reds vs. Mariners prediction: Who will win and cover?
Our independent predictive model currently gives the Mariners a 52.9% chance of defeating the Reds.
According to our model, the Reds (+1.5) have a 64.3% chance of covering the run line, while the over/under total of 7.5 runs has a 55.7% chance of going over,.
Reds vs. Mariners odds [7/21/2026]
We have researched the best MLB odds in America for this game, which are listed here:
| Bet Type | Reds | Mariners |
|---|---|---|
| Run Line | +1.5 (-220) | -1.5 (+180) |
| Moneyline | +108 | -110 |
| Total | o7.5 (-104) | u7.5 (+102) |
All odds are correct at the time of publication and are subject to change.
Reds vs. Mariners picks and best bet
After matching our predictions against the best available odds, we can reveal our picks for each of the major markets in this matchup. Plus, find our best bet for the game below:
| Bet Type | Pick | Bet Now |
|---|---|---|
| Run Line | Mariners -1.5 | +180 |
| Moneyline | Mariners | -110 |
| Total | Over 7.5 | -104 |
According to our best MLB bets, the top play to make on this game is Over 7.5 total runs.
These picks are based on our probabilities matched against the implied probabilities from the sportsbook odds.
Reds vs. Mariners game-day updates and essential details
Tuesday's MLB matchup between the Mariners and Reds at T-Mobile Park is scheduled to start at 9:40 PM ET.
- Who: Cincinnati Reds vs. Seattle Mariners
- Date: Tuesday, July 21, 2026
- Time: 9:40 PM ET/6:40PM PT
- Venue: T-Mobile Park
Conclusion
We predict the Mariners, with a 52.9% win probability, will likely beat the Reds in Tuesday's MLB matchup.
Additional tools and information for betting safely can be found in our Responsible Gambling hub.
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Jason Bevilacqua, an expert in MLB, NHL, NBA, MLS, and NFL, delivers game previews, best bets, and props. Since 2020, as Head of Social and Community at Dimers, he has contributed insightful articles utilizing data-driven models and simulations.
