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How the Mariners Made the 2025 MLB Postseason

Originally posted on New Baseball Media
By Chris Studley | Last updated Sep 25, 2025 7:17 PM ET

The Mariners missed out on the postseason in each of the last two seasons, after Seattle broke through back in 2022. It was a different season for the M’s in 2025, as a superstar catcher and a strong overall pitching staff helped lead the Mariners to a playoff berth and their first division title since 2001.

A home run barrage

From 2022 through 2024, the Mariners finished in the top half of the league in home runs all three seasons. This year, the Mariners are second in the Majors behind only the Yankees, thanks to the “Big Dumper.”

Cal Raleigh, one of Seattle’s key hitters when the Mariners last made the postseason in 2022, hit 60 home runs heading into September 25, setting numerous records along the way. Not only did he break Salvador Perez‘s record for most homers by a catcher but he also broke Mickey Mantle‘s mark for most home runs by a switch-hitter.

And with four games left to go, Raleigh could tie or pass Aaron Judge for the American League record.

The fact that a catcher hit the 60-home run marker is simply remarkable. However, it is worth noting that the Mariners have used Raleigh as their DH for 35 games, simply because his bat is too valuable not to be in the lineup.

There’s not much that needs to be written about Raleigh’s 2025 campaign. It’s been an obviously incredible season. But for the Mariners, it’s been far from a one-man job this season.

Julio Rodriguez tied a career-high for home runs (32). Rodriguez slashed .207/.309/.372 (.681 OPS) in March & April but turned it on afterwards. Randy Arozarena hit 27 home runs, a career-high, for the M’s in his first full season with Seattle.

Jorge Polanco, who had an injury-plagued past few seasons, hit 25 home runs in what was a strong second act for the Mariners. Polanco re-signed with the team back in January after a down year.

Elite pitching

The Mariners’ pitching staff has been a major strength over the past few seasons. Even though the Mariners didn’t make the playoffs in 2024, Seattle had the best starters’ ERA in the league and was top ten among relievers.

On paper, it hasn’t been as strong in 2025. Mariners starting pitchers ranked 14th in ERA (3.97), and 21st in HR/9 (1.3). Although the Mariners have netted plenty of strikeouts (8.8 K/9 – 8th in MLB).

Last year, the star of the rotation was Logan Gilbert. Gilbert has been very good this season, with 168 strikeouts over 126 innings. However, his splits between home and road have been stark this season.

Stat	Home	Road
ERA	2.13	4.74
OPS	.492	.767
K/9	13.6	10.3

Gilbert’s home & road splits for 2025.

Luis Castillo, much like Gilbert, also had stark home & road splits. Opposing batters posted a .580 OPS at home, compared to a .833 OPS on the road.

The one starter who’s been incredible both at home & on the road was Bryan Woo, one of two Mariners All-Star pitchers this season. Woo pitched very well in 2023 and 2024 despite having his innings heavily controlled. The 25-year-old was let loose this season and pitched extremely well, with 198 strikeouts over 186.2 IP.

A pectoral injury has been the only thing to slow Woo down this season, one that could cost him a 200-strikeout campaign.

The bullpen, yet again, has also been a major strength.

Andres Munoz has 38 saves and a 12.2 K/9. Eduard Bazardo, Carlos Vargas, Gabe Speier, and a healthy Matt Brash have provided the depth needed to piece together innings before getting to Munoz.

Bolstered roster

Go back two months in time and look back at the Mariners’ run differential. Seattle’s run differential was +18, not terrible by any stretch but a sign that despite the likes of Raleigh, Rodriguez, and Polanco, the Mariners needed some offensive reinforcements.

President of baseball operations Jerry Dipoto loves to make moves, and he made several in July to help stack the deck in the Mariners’ favor.

The Mariners made two separate trades with the Diamondbacks, one to add Josh Naylor to fill a hole at first, and the other to re-acquire third baseman Eugenio Suarez from Arizona. Seattle traded Suarez to the Diamondbacks after the 2023 season.

It’s been a complicated run for Suarez, who did hit 12 home runs over two months with the Mariners. That number is a tie in the top-20 since August 1. On the other hand, his 36.2% K% is among the bottom 10 of the league (min. 125 PA).

Naylor’s been a smashing addition for the Mariners. The soon-to-be free agent hit .291 with nine home runs and picked up some big hits, including a bases-clearing double on the day Seattle clinched a playoff berth.

Fast forward to September 25, and the Mariners had the fourth-best run differential in the American League, behind only the Yankees, Red Sox, and Rangers.

Seattle also received further help late in the summer when Victor Robles returned from a serious shoulder injury that shelved him for most of the year. He hasn’t been as good offensively — but he has been good defensively.

What to expect in October

The time is now for the Seattle Mariners.

Seattle has a rotation built for October, between Woo — provided he’s healthy, as well as George Kirby, Castillo, and Gilbert. And given that contracts for Kirby and Gilbert will be due soon, the Mariners may not have many shots left with this group before making tweaks.

On paper, the Mariners have the lineup depth and arms to not only do damage in October but do something never done in franchise history: win a World Series title. Time will tell whether that happens. But, securing a bye for the ALDS will move the team one step forward.

This article first appeared on New Baseball Media and was syndicated with permission.

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