The Seattle Mariners’ 40-man roster is now completely filled.

Monday marked the deadline for several different types of transactions for MLB teams. This was the deadline for players or teams to exercise their options, for teams to submit qualifying offers to eligible players, and for clubs to activate players from the 60-day injured list and place them on the 40-man roster.

The Mariners made two of the three transactions on Monday.

Seattle There were no free agents eligible to receive a valid offer, meaning the only action left was to activate three players (Sam Haggerty, Matt Brash, Jackson Kowar) from the injured list and wait to find out if outfielder Mitch Haniger exercised his offer. $17.5 million player option.

Barring a confusing few hours with no confirmation as to whether Haniger exercised his player option after 2pm PT, it was unlikely anything unexpected would come up for the Mariners heading into Monday.

Except for one thing.

Seattle optioned the contract of 26-year-old pitcher Blas Castano from the team’s Triple-A affiliate on Monday. With the addition of Castano, Kowar, Haniger, Brash and Haggerty filled out the team’s 40-man roster.

Francys Romero initially reported the roster move.

Castano played 29 games for the Rainiers and their Double-A affiliate Arkansas Travelers in 2024, making 26 starts. He posted a 4.38 ERA with 108 strikeouts in 125.1 innings pitched.

Castano was originally signed by the New York Yankees as an international free agent out of the Dominican Republic on June 1, 2018. He was released by the organization on August 8, 2023 and signed by the Mariners on August 11, 2023.

Castano is an interesting choice for the 40-man roster, especially considering he has been used mostly as a starting pitcher since joining the Seattle organization. Considering the Mariners’ elite starting rotation, this could indicate the team wants to see Castano in spring training. This could also indicate that the team envisions Castano being used as a reliever in the future.

This could also have been a way to prevent the team from taking Castano in December’s rule 5 draft.

Whatever the reason, it won’t be long before Seattle fans take a good look at Castano.

HANIGER OFFICIALLY USE PLAYER OPTIONS: After several hours of confusion, it was confirmed that the Seattle Mariners outfielder had exercised his player option for 2025. CLICK HERE

FORMER MARINERS OUTFIELDER, WE JOIN THE MARINERS’ BEST COMPETITOR: The 2024 World Series champion and former Seattle Mariners outfielder was acquired by the team’s biggest rivals on Monday. CLICK HERE

RALEIGH JOINS THE PRESTIGIOUS LIST OF MOORE FRANCHISE GOLD GLOVE HONORIES: Seattle Mariners catcher Cal Raleigh and infielder Dylan Moore are Gold Glove winners on a list that includes several team legends and Hall of Famers. CLICK HERE

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