Mariners vs. Astros prediction: Seattle favored to win Sunday's MLB matchup [9/21/2025]

The Houston Astros will square off with the Seattle Mariners in MLB action at Daikin Park on Sunday, starting at 7:10PM ET.

Jason Alexander (4-1, 4.04 ERA) will be on the bump for the Astros, while the Mariners have opted for Logan Gilbert (5-6, 3.52 ERA).

Based on updated simulations, Dimers' advanced MLB model predicts the Mariners as the most likely winner of today's game.

"Using the most recent data, our experts ran 10,000 simulations of Sunday's Mariners-Astros game," said Dimers' Chief Content Officer, Nick Slade.

"After accounting for recent updates and other variables, our prediction shows the Mariners with a win probability of 55%, while the Astros have 45%."

For further insights into Sunday's matchup, including best bets and picks, visit our interactive Mariners vs. Astros predictions page.

Astros vs. Mariners prediction: Who will win, cover the run line?

Using trusted machine learning and data analysis, we have simulated the outcome of Sunday's MLB matchup between the Mariners and Astros 10,000 times as part of our MLB predictions coverage.

Our famous predictive model currently gives the Mariners a 55% chance of defeating the Astros.

According to our model, the Astros (+1.5) have a 58% chance of covering the run line, while the 8.5-run over/under has a 56% chance of going over.

Mariners vs. Astros odds [9/21/2025]

We have sourced the best MLB odds in America for this game, which are listed here:

Bet Type	Mariners	Astros
Run Line	-1.5 (+115)	+1.5 (-126)
Moneyline	-148	+126
Total	o8.5 (-105)	u8.5 (-114)

All odds are correct at the time of publication and are subject to change.

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Mariners vs. Astros picks and best bets

Our model's biggest edge in today's Mariners vs. Astros matchup is on the run line.

Our expert predictions, aligned with the best odds, reveal the best MLB picks and MLB best bets for every game throughout the season.

Unlimited access to our complete suite of picks, including this one, is available via Dimers Pro.

Calling Our Shot's best bets video

Calling Our Shot produces daily MLB betting content, including the latest predictions featured below.

Mariners vs. Astros game-day updates and essential details

Sunday's MLB matchup between the Astros and Mariners at Daikin Park is scheduled to start at 7:10PM ET.

• Who: Seattle Mariners vs. Houston Astros
• Date: Sunday, September 21, 2025
• Time: 7:10PM ET/4:10PM PT
• Venue: Daikin Park

Dimers' in-depth preview of Sunday's Mariners vs. Astros matchup includes our prediction, picks and the latest betting odds.

Before making any Mariners vs. Astros picks, be sure to check out the latest MLB predictions and betting advice from Dimers Pro.

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Conclusion

We predict the Mariners, with a 55% win probability, will likely beat the Astros on Sunday.

AI and automation have enhanced this article to quickly deliver accurate Mariners vs. Astros insights, with human oversight ensuring high editorial quality. Our predictions are sourced from the latest data to help you make informed decisions. For additional resources and advice on responsible gambling, please call 1-800-GAMBLER.

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