Mariners Have an Alarming Range Problem Wrecking Their Run Prevention Formula

Seattle’s defense is creating a quieter problem than the error column suggests.

Apr 12, 2026; Seattle, Washington, USA; Seattle Mariners center fielder Julio Rodriguez (44) catches a pop fly ball during the fifth inning against the Houston Astros at T-Mobile Park. Mandatory Credit: Steven Bisig-Imagn Images | Steven Bisig-Imagn Images

We already know the Mariners can make life hard on their pitching staff with the bats. That has been part of the deal for years. But this year, the problem has an extra layer.

The Mariners are not just failing to back their pitchers with enough offense. They’re also not backing them defensively, and for a team that keeps selling itself on run prevention, this is pretty uncomfortable.

If the whole idea is to build around pitching, defense, and clean baseball, then the defense can’t afford to be this shaky. It definitely cannot be sitting near the bottom of the league in Fielding Run Value while the rotation is still being asked to carry the weight of the entire operation.

According to Baseball Savant’s Fielding Run Value leaderboard, the Mariners are at minus-11, ranking 29th among MLB teams. Only the Angels were worse, which feels especially rich considering Jo Adell robbed the Mariners of three home runs by himself.

And the split plays an important role. Cal Raleigh and the Mariners’ catching group are actually helping. Seattle is at plus-three catching runs, with Raleigh showing positive value in framing, throwing and blocking. That part of the defense is not dragging them down. If anything, it’s keeping the overall picture from looking even uglier.

The real issue is everything happening in front of and around the pitching staff.

The Mariners are at minus-14 in infield/outfield runs, and the loudest number is the range column: minus-13. Their arm value is neutral. Their double-play value is only slightly negative. So this isn’t really about a team wildly throwing the ball around or booting everything in sight. It’s more frustrating than that. It’s about balls finding grass. 

Mariners Defensive Concerns Add Another Layer to Their Familiar Offensive Frustration

The traditional numbers do not make the defense look like a complete mess. That’s why Fielding Run Value tells a harsher story than fielding percentage. The Mariners are not being punished for obvious mistakes. It’s the plays they aren’t making, and that’s a brutal flaw for a team built this way. 

Seattle can live with a few defensive tradeoffs if the lineup is consistently carrying its end. It can live with an uneven offense if the defense is turning batted balls into outs at an elite level. What it can’t do is ask the pitching staff to survive both at the same time.

That’s where this starts to feel like a roster identity problem. The Mariners have acquired plenty of talent the last several seasons. They have power, athleticism, versatility and upside scattered across the roster. But the question is whether enough of those pieces actually fit together as two-way answers. Too often, Seattle still feels caught between ideas: chasing more offense without fully protecting the defense, valuing run prevention without actually fielding like a run-prevention team.

The number itself can change by next week. The bigger concern is harder to shake: Seattle still looks like a roster built from competing priorities instead of one clear identity.

Maybe the Fielding Run Value ranking improves. Early-season defensive metrics can be noisy, and nobody needs to pretend one snapshot today tells the entire story. But the roster question underneath it is not noisy at all. 

And until the Mariners figure out whether this roster is built to hit, built to defend, or somehow built to do both, the pitching staff is going to keep carrying a burden that feels heavier than it should.