The No. 9 prospect in baseball (per MLB Pipeline) and the top prospect in the Seattle Mariners farm system, infielder Colt Emerson, entered this spring with an opportunity to make the team's Opening Day roster.

Before the Mariners acquired 2025 All-Star Brendan Donovan in a trade with the St. Louis Cardinals, it was assumed that Emerson and since-traded third baseman Brendan Donovan were the leading candidates to open the season as the team's starting third baseman.

Since acquiring Donovan, he's been the de facto third baseman and Cole Young has cemented his spot at second base. Even still, Seattle seemed open to the idea of Donovan moving between second and third. JP Crawford could also miss a short amount of time with a shoulder injury, which would have opened a roster spot for Emerson.

Alas, Emerson's spring, at least from the major league side of things, came to an end on Saturday. The Mariners re-assigned Emerson to minor league camp and optioned outfielder Rhylan Thomas to the Triple-A Tacoma Rainiers.

According to a post on "X" from Seattle Times reporter Adam Jude, Emerson will begin the season with Tacoma.

Emerson had an impressive spring and it's likely a matter of "when," rather than "if," the former first round draft pick will make his major league debut this season.

The 20-year-old infielder slashed .268/.340/.488 with an .828 OPS in 18 Cactus League games and hit a double, a triple and two home runs with eight RBIs.

Both Seattle president of baseball operations Jerry Dipoto and general manager Justin Hollander have already said that Emerson factors into the team's plans in 2026. And based off his last year of pro ball, it's easy to understand why.

The top 10 prospect began last year with the High-A Everett AquaSox and ended the year with the Rainiers. He was also on the team's major league postseason taxi squad as it made its run to Game 7 of the American League Championship Series.

In '25, Emerson slashed .285/.383/.458 with an .841 OPS and hit 28 doubles, six triples and 16 homers with 78 RBIs across 130 games at the High-A, Double-A and Triple-A levels.

Emerson may begin '26 in the minor leagues but it likely won't take him long to reach the majors.

There's recent precedent of a young infielder performing well in spring, starting the year in the minors and making his big league debut shortly thereafter. Williamson made his major league debut April 15, 2025.

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