Prospect's unexpected hot start could shift Mariners' plans for future infield

When thinking of the future of the shortstop position for the Mariners, Colt Emerson rightfully occupies most of the attention. He's the organization's best prospect and the No. 6 prospect in baseball. The defensive mishaps of J.P. Crawford are giving his chances of being called up a meaningful boost and thanks to the contract extension he signed this year, he'll be around for quite some time.

However, Emerson could have a little more competition for the starting job than some may have initially thought.

Felnin Celesten's strong start in High-A sets him up as a candidate for Seattle's shortstop job

Felnin Celesten has been a highly-touted name since he was signed as an international free agent in 2023. Ranked as the second-best player in his class, the Mariners spent $4.7 million on him, accounting for a big chunk of their $6.4 million bonus pool. His first year in the complex league was a great success, but his first full minor league season had some underwhelming results.

He spent most of 2025 with Single-A Modesto and managed a modest 108 wRC+, losing much of his power production and posting an ISO of just .099 over 424 plate appearances. His hitting suffered even more in a limited sample of High-A plate appearances, as his strikeout rate jumped to 31.3%. Although he didn't quite live up to the hype in his first full season of professional baseball, he started 2026 as the organization's No. 7 prospect thanks to the sheer upside of his skillset.

After 108 plate appearances in High-A, Celesten has already taken a big step forward. He has a much better 125 wRC+ and is exercising improved plate discipline, walking at a 15.7% clip against a 19.4% strikeout rate. Most importantly, his power is back and while still lower than his days in the complex league, has a .420 slugging percentage.

At just 20 years old, the Mariners don't need to rush him but a promotion to Double-A is imminent if he keeps up the good work. If he manages to get there and thrive, a call-up is the natural next step but where would he fit on the depth chart?

Because of his contract and the fact that he's simply further along in his development, Emerson will get first dibs on any shortstop opportunities before Celesten has a chance. However, with a solid arm and good defensive fundamentals, he could play other positions in the infield if needed. If Celesten's timeline doesn't line up with Seattle's roster availability, the organization could always trade him away to patch up weaker parts of the team.

But just because he's having a good stretch of games in High-A doesn't mean that he's guaranteed to make the majors. While it's always exciting to see another one of the team's young prospects thrive in the minor leagues, there are more than a few hurdles to overcome before the front office is forced to make any real decisions.

Even if he doesn't manage to become a core piece of Seattle's infield, his success will, at the very least, be another winning example of the Mariners' player development abilities.

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