The Seattle Mariners have spent the offseason addressing some key areas, but if they truly want to maximize their potential in 2025, there’s still work to be done. The team made significant strides offensively down the stretch last season, but relying on those improvements alone to carry over into the new year would be a dangerous assumption.
With Julio Rodríguez, Victor Robles, and Randy Arozarena locked in as the starting outfield, the Mariners must now turn their attention to the infield and designated hitter (DH) spots. While club president Jerry Dipoto has hinted at internal solutions, there are three crucial moves Seattle should make before Opening Day.
Each of these moves would help balance the lineup, add much-needed power and consistency, and elevate the Mariners’ chances of contending in the AL West.
Trade for Triston Casas
One of the Mariners’ biggest question marks is first base, where the team has yet to establish a long-term solution. While Luke Raley emerged as a potential option last season, the Mariners should aim higher—and Boston’s Triston Casas presents a golden opportunity.
Casas, a 6-foot-5 left-handed slugger, has already proven his ability to hit for power and get on base. Over his first two MLB seasons, he has posted an .830 OPS with 42 home runs in just 840 plate appearances. More importantly, he could be a cornerstone bat for Seattle’s future at just 25 years old and under team control through 2028.
The Red Sox, meanwhile, just signed Alex Bregman, and there are growing talks of moving Rafael Devers to first base, but not without controversy. If that happens, Casas could become available via trade—and the Mariners have the pitching depth to make a deal happen.
While parting with one of Seattle’s young arms would be tough, securing a young, cost-controlled first baseman with elite offensive potential is worth the price. Casas would provide power, plate discipline, and long-term stability at a key position, something the Mariners desperately need.
Sign JD Martinez to strengthen the DH spot
One of the most glaring issues in Seattle’s lineup has been a lack of consistent production at designated hitter. The Mariners need a veteran bat capable of delivering power and clutch hitting, and JD Martinez fits the bill perfectly.
Even at 36 years old, Martinez remains one of the game’s most reliable offensive threats. In 2024, he hit 33 home runs with an .864 OPS, proving that he still has plenty left in the tank. Adding him to the middle of the lineup would immediately boost Seattle’s run production and provide a feared bat to protect Julio Rodríguez.
Martinez also brings valuable postseason experience, having played in numerous playoff series and won a World Series with Boston in 2018. His ability to hit in high-pressure situations would be a game-changer for a Mariners team looking to break through in October.
The biggest benefit of signing Martinez? It wouldn’t require giving up assets in a trade. Seattle has the payroll flexibility to make a one-year, incentive-laden offer, giving Martinez a chance to chase another playoff run while ensuring the Mariners have a dependable DH.
Sign José Iglesias to upgrade second base
Second base has been a revolving door for the Mariners in recent years, and while the team has some internal options, none offer the stability and veteran leadership that José Iglesias brings.
Iglesias enjoyed an outstanding 2024 campaign with the Mets, hitting .337 with a 137 wRC+. His arrival coincided with the Mets’ dramatic turnaround, and while his success was aided by a high BABIP, he remains an elite contact hitter with a proven track record.
Beyond his bat, Iglesias is still a strong defensive presence. With his ability to make consistent plays in the field, he would help shore up Seattle’s infield defense, which remains a concern heading into 2025.
At 35 years old, Iglesias wouldn’t be a long-term solution, but he fills an immediate need while the Mariners develop younger options. Signing him would give Seattle a veteran infielder who knows how to win—a quality that can’t be overstated.
The Mariners have built a strong foundation, but their 2025 roster isn’t complete yet. Trading for Triston Casas, signing J.D. Martinez, and adding José Iglesias would provide the offensive firepower and veteran presence needed to contend in the AL West.
Seattle’s pitching remains a strength, and their outfield is set, but failing to upgrade their infield and DH spot would leave the team vulnerable to another season of offensive struggles.
If the Mariners truly want to compete with the Astros and Rangers, they can’t afford to sit back and hope for internal improvement. These three moves would give them the balanced, deep lineup necessary to make a legitimate postseason push—and finally bring playoff baseball back to Seattle.
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