The Seattle Mariners haven’t had a “true” first baseman in a long time. Someone who hits for a decent average with exceptional power numbers is a rarity in the Pacific Northwest.
The last Mariners first baseman to hit over 30 home runs in a season was Russell Branyan in 2009. Nowadays, this archetype does not want to make the journey to Seattle. With the longer plane rides, the cold weather, and the Marine Layer, it’s almost a hitter’s nightmare. Not to mention the odd batter’s eye at T-Mobile Park. We already know how good Seattle’s pitching lab is and has been. The offense continues to be their main problem, and with name after name leaving the drawing board, they’ll have to pivot away from the power-hitting profile to someone who will help the offense any way they can.
With no real starting first baseman nailed down, here are some candidates to take the reigns in 2025.
Mariners First Baseman Candidates for Next Season
1. Pete Alonso, Free Agent
A signing that would split the fanbase, Pete Alonso undeniably does one thing incredibly well: hit home runs. Since he burst onto the scene in 2019 with his 53 home run rookie year, he’s yet to hit under 30 when playing more than 100 games (16 in the shortened 2020 season). His power would sit nicely in the middle of the order for Seattle, and provide some solidity in the lineup, taking pressure off of guys like Randy Arozarena, Cal Raleigh, and Julio Rodriguez. His biggest downfall is his strikeouts. He’s posted a strikeout rate above 22% in four of his six big league seasons. That would make him right at home in a lineup that had nine players strike out more than 100 times in 2024.
Alonso is not the high-average bat Seattle needs, but his power and ability to draw a walk would be great tools to help the guys around him and move the order along. However, it remains doubtful that John Stanton would shell out the money needed to make him the new Mariners first baseman.
2. Yandy Díaz, Tampa Bay Rays
Yandy Díaz is going into his age 33 season and will be a free agent after 2025 if his 2026 team option is not picked up. His $8 million salary is perfect for a budget-afflicted team like Seattle.
A consistent hitter, Díaz would bring an average likely above .260 to Seattle, something they desperately need. While Díaz had the worst walk rate of his career last year, his strikeouts were down from 2023, something Seattle also desperately needs. His 10-15 home runs aren’t exceptional, but you have other guys like Raleigh or Rodriguez who can pull that weight. He’s essentially what Seattle had hoped Ty France would be. He would come at a price considering Tampa Bay has offloaded Arozarena, Isaac Paredes, Austin Shenton, and Jose Siri in the last two seasons.
3. Vinnie Pasquantino, Kansas City Royals
Vinnie Pasquantino is Jerry Dipoto‘s dream: someone who is young and controllable. Now 27, Pasquantino had his first full major league season in 2024 and did not disappoint. He notched career highs in hits, home runs, RBI, and walks last year. Another high-average bat that would slot into the middle of the lineup, Pasquantino also offers a power threat, with 19 home runs last year.
It wouldn’t make a ton of sense for Kansas City to trade him, especially to someone like Seattle, who is a potential postseason matchup. Kansas City is a young team with talent bursting from the seams, but they need something Seattle can offer: pitching. Plus, trading Pasquantino would allow them to shift Salvador Perez to first base and save his knees, and also give budding Freddy Fermin more work behind the dish. This trade might make more sense than it seems.
4. Vladimir Guerrero Jr., Toronto Blue Jays
With the star that Vladimir Guerrero Jr. is, this trade is a long shot, especially because there isn’t a lot of love between these two teams. They’ve always had tension since Toronto’s Western Canada-residing fans flood the stadium when they play in Seattle. Not to mention some social media beef in 2022, before they even met in the postseason.
However, the Mariners have been circling Vladdy since the end of the 2023 season, with reports from Jon Heyman even coming out about potential “aggressive” trade packages being offered at the deadline in 2024.
The Blue Jays aren’t a great offensive team, and it would hurt to lose one of, if not their best player. But, they also need pitching. You don’t really know what you’re going to get out of Alek Manoah in 2025, and guys like Kevin Gausman, Chris Bassitt, and José Berríos, while good, are all on the wrong side of 30.
Toronto also has an incredibly depleted farm, ranking 24th on MLB’s farm rankings. Seattle certainly has the pitching and the prospects to tempt Toronto into a deal.
5. Luis Arráez, San Diego Padres
Long-time trade partners, the Padres are in dire need of help in their farm system. MLB has them ranked 28th overall after dealing 12 of their top 21 prospects at the deadline in 2024. Seattle, ranked ninth, certainly has the prospect capital to bolster San Diego’s farm. With some okay pitching, a trade package for Luis Arráez would have to be more prospect-heavy.
Arráez is Seattle’s dream hitter. Offering a high average with infield versatility, he could fill in just about anywhere Seattle needs him to. It’s a shame he can’t hit in every spot in the order. Cushion him with Rodriguez, Raleigh, and Arozarena, and you’ve got what sounds like a recipe for success brewing in the Pacific Northwest.
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