Free MLB picks today: Sunday's MLB best bets include Mariners vs. Astros play [9/21/2025]

Today’s free MLB picks for September 21, 2025 are here, with Sunday’s MLB best bets fueled by tens of thousands of predictive simulations analyzing the latest odds and matchups.

These MLB best bets include matchups like the Mariners vs. Astros game at 7:10PM ET, with this article updated throughout the day to feature the highest-probability plays based on thousands of data-driven simulations from our predictive analytics model.

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List of MLB best bets tonight [9/21, updated 7:03PM ET]

After digging deep into the numbers and conducting thousands of simulations, our independent predictive analytics model has identified the best baseball bet for Sunday, September 21, 2025.

Mariners vs. Astros over 8.5 runs (-105)

• Probability: 55.6%
• Edge: 4.3%
• Matchup: Mariners vs. Astros (7:10PM ET, Sunday)

Our model has pinpointed a high-probability MLB betting opportunity tonight, which comes in the Mariners vs. Astros game. We recommend an over/under bet on over 8.5 runs at -105 odds, with our analysis showing a 55.6% chance of hitting and a compelling edge of 4.3%.

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List of upcoming MLB games to bet on [9/21/2025]

• Mariners vs. Astros (7:10PM ET, Sunday)
• Red Sox vs. Rays (7:35PM ET, Sunday)

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More on MLB

The bets on this page form part of our MLB player props and MLB best bets series.

For more MLB betting content, we have MLB trends for every game, as well as daily MLB betting news and the latest World Series odds and predictions.

Conclusion

Our MLB best bets are locked and loaded for September 21, 2025, featuring plays such as over 8.5 runs in the Mariners vs. Astros matchup. Powered by advanced simulations, these picks are here to boost your betting game.

This article, enhanced by AI and automation, aims to deliver accurate MLB insights quickly, with human oversight ensuring high editorial quality. Our predictions are sourced from current data to help you make informed decisions. For additional resources and advice on responsible gambling, please call 1-800-GAMBLER.

All odds and probabilities in this article are correct and accurate at the time of publication.

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