Sep 21, 2025; Houston, Texas, USA; Seattle Mariners relief pitcher Matt Brash (47) and teammates celebrate after defeating the Houston Astros at Daikin Park. Mandatory Credit: Thomas Shea-Imagn Images Thomas Shea-Imagn Images

Mariners' Magic Number To Clinch Division, First-Round Bye After Sweeping Astros

Originally posted on Fastball on SI | By Jackson Roberts | Last updated Sep 22, 2025 8:18 AM ET

The Seattle Mariners sent a loud message to the rest of Major League Baseball over the weekend, while simultaneously putting themselves in prime position for a first-round playoff bye.

With a three-game sweep of the Houston Astros, the Mariners seized control of the American League West. Seattle (87-69) now has a three-game lead on Houston (84-72) with six games to go, with the tiebreaker in hand.

If that wasn't good enough news, thanks to the Detroit Tigers' (85-71) six-game losing streak, the Mariners are also in the driver's seat for the No. 2 seed in the AL postseason, which would include a free pass directly to the Division Series.

Mariners' updated magic numbers to clinch division and bye

The AL West should be the Mariners' grasp, barring a collapse in the season's final week. With matchups against the Colorado Rockies and Los Angeles Dodgers on deck, Seattle needs just three wins or Astros losses to secure its first division title since 2001.

The Mariners own the tiebreaker over Detroit as well, so the magic number to clinch a first-round bye is four (assuming the Toronto Blue Jays (90-72) lock up the American League East and relegate the New York Yankees (88-68) to the No. 4 seed).

The Cleveland Guardians trail the Tigers by one game, so they're in the picture as well. Seattle's magic number to finish ahead of Cleveland is three.

Because the Astros and Guardians are tied for the final Wild Card spot, the magic number to clinch a playoff berth remains at three as well. Thankfully, Cleveland plays Detroit this week, so one of the AL Central teams Seattle is currently ahead of is guaranteed at least two losses.

Here's the bottom line: if the Mariners go 3-3 this week against the Rockies and Los Angeles Dodgers, they'll guarantee a division title and almost certainly earn a first-round bye as well. A 2-4 record would likely accomplish both of those objectives as well.

In other words, it's going to take an epic collapse to undo the brilliant work the Mariners did this weekend. September is all about seizing control of your destiny, and that's just what Seattle did in Houston.

More MLB: Mariners Seize Control: Magic Number, Playoff Odds After Pivotal Win Vs. Astros

This article first appeared on Fastball on SI and was syndicated with permission.

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