Unexpected Andrés Muñoz successor is hiding deep in Mariners' farm system

Although some key members of the Mariners have been warming up, a few have still failed to come out of their early-season skid. The most notable is Cal Raleigh, whose offensive output has cratered following a record-setting MVP season, but closer Andrés Muñoz has looked uncharacteristically shaky as well. He has a 6.00 ERA and 3.80 FIP across 15 innings.

The team has temporarily offloaded closer duties to Jose A. Ferrer, but Muñoz isn't going to be gone for long. His underlying numbers do suggest that he has been better than his ERA would have one believe and he's on an incredibly team-friendly contract with two remaining club options. However, when the team does eventually decide to rely on a different arm in the ninth inning, an unsuspecting pitching prospect could step in to fill his place.

Brock Moore has been dominant out of the bullpen for High-A Everett so far this season

Moore was a seventh-round pick in the 2024 draft and was somewhat of a late bloomer. After two unimpressive years of junior college, he transferred to Menlo College for two seasons and then to Oregon for his final year of eligibility. Over 114 college innings, he had a lukewarm 4.97 ERA. Things didn't get much better in his first full minor-league season which saw him post a 9.64 ERA over 18.2 innings before being sidelined with a dislocated right shoulder. Despite these challenges, 2026 has been a completely different story.

He has already pitched a total of 12.1 innings this year and is sitting at a 1.46 ERA and 1.30 FIP. He has an absurd 60.5% strikeout rate with a walk rate of just 4.7%, ideal qualities for a top-notch closer.

His impressive work has caught the eyes of the organization's scouts and a promotion to Double-A Arkansas seems imminent. If he keeps it up, he could be knocking on the doors of the majors and be poised to take over as the team's new closer.

Of course, the Mariners will need to see far more than 12 innings of successful High-A pitching before they call him up and then he'll need to prove himself as a regular bullpen arm before taking the ball in high leverage. It's a bold hypothetical that requires a few things to fall in place but it may be closer to reality than one might initially think.

When it comes to pitching development, the Mariners are one of the best in the business and the 2025 draft class already looks like a preview of what the team's rotation could look like in just a few years. This current iteration of the front office has always preferred to find talent from within the system instead of paying big bucks on external talent and with the current market premium on closers, Brock Moore is looking like a huge potential win on the field and for the payroll if he continues his rise to the top.

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