Mariners Prospects That Stood Out This Spring

When prospect lists were slowly released this winter, Rhylan Thomas was rarely found among the top names. FanGraphs had him outside their top 25 Mariners prospects, while MLB snuck him in at 23. But among a deep crop of outfield prospects, Thomas has done the most to give himself an outside shot of making the roster in case of injury.

Brennen Davies has turned the most heads with some ridiculous power numbers this spring. But quietly, Thomas has now had the most productive camp. With a .472/.524/.778 slash line, he has been consistently raking in Arizona. Across 42 plate appearances, this is now a meaningful sample size. His power production has been standout, with his OPS at 1.302 and his wRC+ at 231. Beyond these power numbers, his underlying metrics are even more impressive.

Plate Approach

Compared to Davies, who is slugging at a similar rate, his strikeout rate is 27.5%, while Thomas is at a borderline impossible 7%. That level is unlikely to hold; however, his plate discipline shows a mature approach that can translate into future major league success if maintained. His swinging strike rate this spring is a league-best 2.6% for hitters with more than 40 plate appearances. With an O-Swing% at a career-low 25%, he is consistently making strong decisions at the plate. When he swings, he makes quality contact: 35% of his hits are line drives, and 41% go to the opposite field.

This demonstrates the quality of his approach, and paired with his ability to play center field, it gives him a realistic path to contributing at the major league level. While a roster spot would likely depend on injuries, his combination of plate discipline and contact profile has positioned him as a credible next option within a crowded outfield group.

Michael Arroyo

Despite a shortened camp due to his participation in the WBC, infielder Michael Arroyo still stands out as a clear performer. With only 16 plate appearances, it is difficult to draw firm conclusions from his statistics. However, after such a hot start with the bat, there were clear expectations as he went to get meaningful at-bats in a major tournament. While Colombia did not progress out of the pool stage, Arroyo still proved to be one of their elite performers and continued to stand out.

Across Spring Training and WBC play, Michael Arroyo logged 34 plate appearances and produced a .292/.469/.542 slash line, resulting in a 1.011 OPS and reaching base at an elite clip. His eight walks in that span (23.5% BB rate) underline advanced plate discipline, consistently controlling the zone against older competition. While the power output comes in a small sample, the combination of on-base ability and strike-zone judgment is the more reliable indicator of his offensive profile and likelihood of success at the major league level.

Coming into Spring Training, Arroyo and Lazaro Montes were seen as the next high-profile Mariners prospects after Colt Emerson, and their rankings diverged significantly depending on the publication. However, following this spring, Arroyo has proven to have a much more advanced hitting approach and is more developed as a hitter, closer to major league readiness. Arroyo was identified as a player to keep a close eye on in the WBC following his hot start to Spring Training. His at-bats on the global stage only helped further raise his profile as we head into the 2026 season.

Colt Emerson

In a position battle with Cole Young, one that never seemed in his favor without something extraordinary happening, Colt Emerson will more than likely start the season on the outside looking in. Despite this, Emerson has shown he is close to making the jump and has made a very strong impression during Spring Training.

Across his 44 plate appearances, Emerson has shown a well-rounded offensive profile. He is a contact-oriented bat with a plus hit tool and the potential for power in the future. He maintained solid plate discipline even at a higher level. Colt Emerson posted a .282/.341/.513 slash line (.854 OPS), pairing his expected hit tool with emerging power production, as shown by a .231 ISO. Long regarded for his high-floor contact ability, Emerson’s performance suggests growing impact at the plate, even with a relatively modest 9.1% walk rate and 20.5% strikeout rate. Continued power growth would significantly elevate his long-term offensive ceiling.

Cole Young’s impressive spring means he will likely start in Triple-A, barring any injuries to the infield. However, Emerson showed as much as he could have this spring. His introduction to the Mariners roster is now a matter of when, rather than if.