Newest Mariners pitcher is a textbook example of a mop-up guy

What exactly is a mop-up guy? The technical term is a long reliever and they're usually brought out of the bullpen for more than a few innings. However, if they're primarily brought into the game when the chances of victory are slim, they've been unofficially demoted to being the mop-up guy. More often than not, these roles are held by pitchers with the stamina and arsenal to be starters but without the stuff to be trusted every five days.

Cooper Criswell, who the Mariners acquired for cash last week, fits that definition. He was selected in the 13th round of the 2018 draft by the Angels and had an OK minor league career that spanned six seasons and 465.1 innings. He was being groomed as a starter and was a part of the Red Sox rotation in 2024, but struggled to maintain his spot in the majors in 2025.

Cooper Criswell should be a perfect mop-up guy for the Mariners

Criswell is a pitcher with a low arm slot, which limits his velocity but allows him to maximize soft contact with his strange arsenal. His average fastball velocity was just 89.4 mph last season, but because it's a sinker with an awkward delivery, it allows him to consistently generate soft contact, placing him in the top bucket for average exit velocity and ground ball rate.

On the other hand, his lack of velocity doesn't grant him many missed bats. He had a whiff rate of just 14.9% and strikeout rate of just 11.3% last year, but pitching to contact is exactly what he's trying to do. His arsenal contains a changeup, cutter, sinker, and sweeper, all of which have whiff rates below 25% and all of which are pitches typically designed to induce ground balls.

For the Mariners, this isn't an attempt to fill a crucial role in the bullpen. They already have a plethora of talented arms, and someone like Criswell simply isn't going to compete for a meaningful spot on the depth chart. However, off days are rare in a 162-game season and Dan Wilson will need to rely on someone to give the other relievers a break, especially when the game is already out of reach.

The trade to pick up Criswell is one of a few smaller trades the team has made recently, but the team is yet to make another impactful trade despite having all of the pieces to do so. Perhaps the front office is truly that confident in their roster as it stands, or perhaps there simply isn't a market for the players they're interested in.

Either way, this acquisition adds something to the big league roster, but it probably isn't exactly what the team needs right now.