Mariners Acquire Cooper Criswell to Bolster Rotation Depth

This article takes a look at the Seattle Mariners’ latest depth move: they’ve picked up right-hander Cooper Criswell from the New York Mets for cash considerations. Let’s dig into Criswell’s career, his recent numbers, and why Seattle decided to designate left-hander Jhonathan Díaz for assignment to make space.

Mariners Add Low-Cost Pitching Depth

The Mariners made a low-profile but smart move by acquiring Cooper Criswell, a 29-year-old righty who’s bounced between starting and relieving. Seattle sent cash to the Mets, who’d just DFA’d Criswell after picking up Freddy Peralta and Tobias Myers.

To make room, Seattle designated Jhonathan Díaz for assignment. Díaz had been lurking as rotation depth but never really found his footing in the majors.

Why Criswell Became Available

Criswell didn’t lose his Mets spot because he pitched poorly—it was just a numbers game. New York’s roster shuffle gave Seattle a shot to grab a useful arm without giving up prospects.

Breaking Down Cooper Criswell’s Track Record

Criswell’s biggest MLB impact came in the 2024 season with the Boston Red Sox. He threw 99 1/3 innings, bouncing between the rotation and the bullpen.

That season showed why teams like having him around as reliable depth. He’s not flashy, but he gets the job done.

2024 Performance Highlights

Criswell leaned on command and ground balls rather than velocity. Here’s a quick snapshot:

He’s the kind of pitcher who can eat innings and keep things from unraveling—honestly, that’s underrated over a long season.

Limited Opportunities in 2025

In 2025, Criswell barely saw big-league time, pitching in just seven MLB games. Most of his work came in Triple-A, where he put up a 3.70 ERA over 65 2/3 innings.

He’s built a reputation as steady, if unspectacular, organizational depth.

Contract and Roster Complications

Boston tried to keep Criswell away from waivers last November by guaranteeing him $800,000 for 2026. That’s a little above the league minimum, which kind of sums up how teams view him: valuable, but not irreplaceable.

Out of Options and On the Fringe

Criswell ran out of minor league options in 2025. Now, teams can’t just send him up and down freely.

He’s also got the right to reject future outright assignments after a previous career outright, so he’s definitely on the roster bubble.

How Criswell Fits in Seattle

The Mariners’ rotation is stacked with:

But depth behind those five? It’s a little shaky. Criswell gives Seattle some insurance as a swing starter or long reliever, spots they’ve had trouble locking down lately.

Bullpen Crunch Could Lead to Tough Decisions

Seattle’s bullpen is crowded, and most guys can’t be optioned. If injuries don’t open a door, Criswell (or someone else) could end up on waivers while the Mariners try to keep things flexible.

What’s Next for Jhonathan Díaz?

Díaz, also 29, steps aside for now after limited MLB exposure. He’s thrown just 46 1/3 innings in the majors.

Like Criswell, Díaz can elect free agency if outrighted. He gets that option because he’s already been outrighted once in his career.

For Seattle, the move looks like a familiar strategy. They keep piling up decent arms, managing risk, and betting that pitching depth will matter over 162 games.

Criswell isn’t flashy, but in today’s game, innings mean something. The Mariners just picked up a few more, and who knows—they might need every last one.

 
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