The Seattle Mariners are intensifying their pursuit of Minnesota Twins infielder Willi Castro to strengthen their infield and bullpen roster before the trade deadline. After recently securing Josh Naylor for the right side of the infield, the Mariners aim to add depth at third base and in relief pitching, with Willi Castro Mariners trade interest resurfacing as a key focus in discussions this week.
Castro, 28, provides Seattle with multi-positional flexibility, primarily covering second base and the outfield but also capable of filling third base roles. His adaptability allows the Mariners to maintain options for pursuing other notable players, such as slugger Eugenio Suárez, while improving their infield reliability on the left side.
Willi Castro’s Performance and Defensive Versatility Enhance His Appeal
This season, Castro has appeared predominantly at second base and corner outfield positions but also holds substantial experience at third base with 532 career innings and a solid history at shortstop, totaling over 1,200 career innings. His switch-hitting ability bolsters the Mariners’ lineup options, contributing a .252 batting average with moderate power shown through 10 home runs and several doubles and triples this campaign.
Currently in the final year of his contract worth $6.4 million, Castro has delivered consistent offensive production since joining the Twins after being non-tendered by the Tigers. Over two-plus years in Minnesota, he has maintained a .251/.336/.401 slash line, solidifying his reputation as a reliable all-around player.
With Seattle’s current internal candidates at third base underperforming offensively—rookie Ben Williamson’s batting line remains limited despite strong defense—the addition of Castro would represent a clear upgrade. Plans for Jorge Polanco to cover third base were derailed due to his knee surgery and ongoing injury setbacks, leaving the Mariners eager to shore up this position.
Mariners Seek Bullpen Reinforcements from Twins’ Reliever Corps
Alongside strengthening their infield, the Mariners have explored Minnesota’s bullpen for impactful late-inning relievers, focusing on right-handers Jhoan Duran and Griffin Jax. Both players are early in their arbitration years and controlled through 2027, making them attractive targets with long-term value.
Duran, well-known for his role as the Twins’ closer, combines a powerful fastball averaging over 100 mph with a splitter-sinker hybrid, the “splinker,” sitting near 98 mph. Despite a slightly reduced strikeout rate this year compared to his career numbers, his 2.47 ERA and robust strikeout percentages mark him as one of MLB’s elite relief pitchers.
Griffin Jax, while less recognized, offers compelling metrics that highlight his potential. Boasting superior strikeout and walk rates relative to Duran and posting a 2.00 FIP and 1.94 SIERA, Jax is arguably among the best relievers statistically. His swinging-strike rate places him alongside the game’s top pitchers, including Aroldis Chapman and Josh Hader, underscoring his elite status despite an inflated ERA influenced by bad luck on balls in play.
Trade Value and Challenges in Acquiring Twins’ Players
Despite clear interest, the Mariners face challenges acquiring both Castro and a top-tier reliever simultaneously, as the asking price for Minnesota’s most coveted assets remains high. According to ESPN’s Jeff Passan, the Twins demand multiple top-100 prospects for either Duran or Jax alone. Adding Castro into the mix would further elevate the cost, forcing Seattle to carefully consider the trade’s structure.
Seattle Times’ Adam Jude notes the Mariners value both Castro and Minnesota’s bullpen arms but recognizes the difficulty in meeting the Twins’ price for such a package. Jude also identifies left-handed reliever Danny Coulombe as a feasible alternative. Coulombe, a seasoned southpaw, currently holds a 1.16 ERA through 31 innings this season and maintains strong strikeout and walk rates, making him a cost-effective option controlled through the season’s end.
Additional Bullpen Options and Mariners’ Prospect Assets
Besides the primary targets, Seattle may explore adding right-handed reliever Brock Stewart. Stewart’s 2.33 ERA and notable strikeout-to-walk ratio over the past season and a half reflect his quality, though his injury history has limited his playing time. His average four-seam fastball velocity exceeds 96 mph, and while his swinging-strike rate is not as elite as Jax’s, it remains well above average among active pitchers.
The Mariners’ willingness to move high-level prospects is a critical factor in these trade talks. Boasting eight of Baseball America’s top-100 prospects, Seattle commands significant leverage but will need to balance present roster upgrades with protecting their future talent pool. The Twins, meanwhile, are not fully rebuilding but seeking to compete again in 2026, preferring prospects nearer to Major League readiness for top trades. Their recent acquisition of a young catching prospect in the Chris Paddack deal exemplifies this approach.
Implications for the Mariners’ Roster and Contention Outlook
The potential addition of Willi Castro and one of the Twins’ high-end relievers could substantially improve Seattle’s infield depth and bullpen reliability heading into the crucial stretch of the season. Castro’s versatility allows the Mariners to address multiple positional needs without sacrificing lineup flexibility, while new bullpen arms like Duran or Jax would enhance late-inning effectiveness.
Balancing these acquisitions against the cost in prospects will be a determining factor in Seattle’s trade strategy, especially as the team strives to emerge as strong contenders. Staying active in these talks signals the Mariners’ commitment to bolstering their roster and maintaining momentum for a playoff push, with outcomes likely to shape their competitive trajectory through 2025 and beyond.