The Seattle Mariners could have another player or two in the World Baseball Classic.

Here are the Mariners playing in the World Baseball Classic

Already sitting at an MLB-high 16 players from their organization on rosters for the 20-team international showcase next month, the Mariners had two players included on a new list released Tuesday. That would be the designated pitcher pool, and one of the names is very notable: Luis Castillo.

The three-time All-Star right-hander is in the designated pitcher pool for the Dominican Republic. The designated pitcher pool allows teams in the WBC to have up to six pitchers who could potentially be called up to their roster if they are one of the eight teams to advance past pool play into the quarterfinals.

Castillo, 33, is the only member of Seattle’s starting rotation that could pitch in the 2026 WBC. If he is called upon by the Dominican Republic, it would mark his WBC debut.

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The Mariners also have left-hander Jhonathan Díaz included on the designated pitcher pool for Venezuela.

Also of note, Jonah Dipoto, son of Mariners president of baseball operations Jerry Dipoto, is in the designated pitcher pool for Italy. The 29-year-old right-hander is a former Kansas City Royals draft pick who pitched last season for the Long Island Ducks in the independent Atlantic League.

Mariners announce two non-roster invites

The aforementioned Díaz was also announced Tuesday as one of two additional non-roster invites for the M’s in spring training.

Mariners’ non-roster spring invites include top two picks of 2025

Díaz, 29, appeared in six games over the past two seasons with the Mariners, spending the majority of that time with Triple-A Tacoma. He was granted free agency in late January after being designated for assignment, clearing waivers and being outrighted to Triple-A.

The other new non-roster invite is outfielder/first baseman Connor Joe. The 33-year-old Joe hit .186 with four doubles in 42 games between San Diego and Cincinnati last season. He has 480 games of experience over six MLB seasons.

So it begins

While it was only pitchers and catchers competing in the World Baseball Classic that were required to report to spring training on Monday, plenty of Mariners are already in Peoria, Ariz., getting work in.

That includes the latest big M’s addition, All-Star utility player Brendan Donovan, as the team shared a picture and video of him Tuesday getting in some cuts in the batting cage.

The new guy is here 👋

Welcome, Brendan! #TridentsUp pic.twitter.com/Wr3obyPUyb

— Seattle Mariners (@Mariners) February 10, 2026

Pitchers and catchers who are not competing in the WBC are set to report Wednesday, with the first full-squad workout set for next Tuesday, Feb. 17. The first Cactus League game isn’t far behind, set for Friday, Feb. 20.

The Hot Stove

You can catch a new edition of the Mariners Hot Stove at 7 p.m. Tuesday night on Seattle Sports 710 AM and the Seattle Sports app. As always, podcasts of the full show will be available at this link or on your preferred podcast app such as Apple or Spotify after it airs.

Here’s the lineup for Tuesday night:

Catch the @Mariners Hot Stove Show tonight on @SeattleSports starting at 7:00! pic.twitter.com/HYcfH2a7NL

— Mariners PR (@MarinersPR) February 10, 2026

More Seattle Mariners coverage

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• ESPN host on Mariners’ Brendan Donovan: ‘You’re going to love this guy’
• Did Mariners pay the right price for Donovan? Morosi weighs in
• Drayer: M’s land All-Star Brendan Donovan after long pursuit
• Seattle Mariners enter 2026 with ‘super high’ expectations