The problem with Mariners’ Andrés Muñoz this season

The position of Seattle Mariners closer hasn’t been in question for the past three seasons, but Andrés Muñoz hasn’t been as effective in 2026 as he was the past two years in All-Star campaigns.

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Muñoz couldn’t protect a one-run lead Sunday, as the Detroit Tigers scored a pair of runs against him in the bottom of the ninth to stun the M’s 5-4.

The Mariners were one out away from a series win, but Kevin McGonigle’s walkoff two-run single turned the tables and handed the AL West leaders a series loss instead.

WALK IT OFF KID pic.twitter.com/HiR8iIdcJE

— Detroit Tigers (@tigers) June 7, 2026

It was the fifth time this season that the 27-year-old Muñoz has blown a save, and with nine converted saves thus far, it’s not a great ratio. For comparison, he had 38 saves to seven blown saves in 64 appearances last season.

Alright, what’s the problem with Muñoz?

Digging into the stats

When you look at the typical pitching statistics, a few things jump out. Most obvious are his 5.40 ERA, 1.37 WHIP and 1.5 home runs allowed per nine innings. Those are all significantly up from his career numbers of a 2.67 ERA, 1.07 WHIP and 0.7 home runs per nine innings.

Muñoz is actually striking batters out at a career-high clip (13.5 strikeouts per nine innings) and walking them less than usual (3.5 walks per nine innings).

What that means is Muñoz has simply been more hittable this year.

On the season, he’s allowing a career-worst 8.9 hits per nine innings, which is almost three more than his career average and 4.7 more than last year.

Opponents are making much more quality contact against him in 2026. The batting average on balls in play against Muñoz is .345 this year, 70 points higher than for his career and almost 100 points higher than last season.

Comparing Muñoz’s Statcast percentile rankings from Baseball Savant of this year and last year really paints the picture of what’s going on. In 2025, of the 16 percentile rankings, 13 of them were red – which is what you want (that indicates above-average). This year, only five of those rankings are red: his breaking pitch run value (85th percentile), fastball velocity (96th), chase percentage (98th), whiff percentage (42nd) and strikeout percentage (97th).

The really concerning stats:

• Pitching run value is 39th percentile (89th in 2025)
• Fastball run value is 21st percentile (47th in 2025)
• Barrel rate is 8th percentile (78th in 2025)
• Hard-hit rate is 7th percentile (55th in 2025)

Andrés Muñoz is getting hit

The answer to what Muñoz’s problem is clear: hitters are hitting him more, and much harder, this year. The tougher thing to answer, though, is why. And it doesn’t make it any easier that his fastball velocity of 98.5 mph is actually up a tick from 2025, as it is for both his sinker and slider.

Back in mid-April, Muñoz told Mariners insider Shannon Drayer of Seattle Sports that he was struggling with his slider.

“Normally I have the grip and throw it as hard as I can, and now I have to find that grip,” Muñoz said. “It’s feeling weird. It’s my best pitch and if I don’t have my best pitch, it is tough to go out there – even if my other pitches are good, you just feel like you don’t go out there with your best weapon.”

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Perhaps that’s continuing to be the issue. He’s actually throwing the slider a bit more in 2026 (55.6%) than he did in 2025 (50.4%), and hitters are doing better against it. In 2025, the slider had a .109 average, .133 slugging percentage and 82.8 mph average exit velocity against Muñoz’s slider. This year, hitters have a .161 average, .339 slugging and 89.5 mph exit velocity against it.

But it’s Muñoz’s fastball (.381 average, .524 slugging) and the lesser-used sinker (.556 average, .556 slugging) that hitters are really doing damage against.

As for what the Mariners do now, it wouldn’t be surprising to see them give some other pitchers a chance to close out games – such as Gabe Speier, Matt Brash and José Ferrer – while Muñoz tries to work through his struggles in lower-leverage situations. At least to this point, though, the M’s have given no indication that a change could be coming.

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