Mariners’ perfect Zac Gallen trade offer to Diamondbacks

Gallen’s track record goes well beyond this season’s surface stats. Across 143 career starts entering 2025, he’s posted a 3.29 ERA, and at his best, he’s been a Cy Young contender, finishing in the top five of NL voting in 2022 and 2023. His durability and ability to miss bats make him a rare commodity: a front-line starter with postseason experience, still under team control through the end of the year. For a Mariners team that has struggled to get over the playoff hump, Gallen offers not just innings and strikeouts, but the kind of October pedigree that can change a franchise’s trajectory.

Arizona, meanwhile, faces a tough decision. With Gallen set to hit free agency after the season and his arbitration salary already at $13.5 million, the D-backs must weigh the value of a qualifying offer against the potential haul of prospects and young talent a trade could bring. Their recent slide in the standings, combined with a roster in transition, makes a deal increasingly likely as the deadline approaches.

The Perfect Trade Proposal

After careful analysis of both organizations’ needs, prospect depth, and the current market for starting pitching, here is the perfect trade proposal that could bring Zac Gallen to Seattle.

Seattle Mariners receive:

• Zac Gallen

Arizona Diamondbacks receive:

• Cole Young
• Emerson Hancock
• Tyler Locklear

This package represents a win-win scenario. For the Mariners, acquiring Gallen is an all-in move that signals their intent to contend now. Gallen’s track record, 3.29 ERA in 143 career starts entering 2025, a Cy Young finalist in 2023, and a proven postseason performer, gives Seattle a legitimate ace to pair with Luis Castillo and George Kirby at the top of the rotation. Gallen’s presence would not only stabilize the staff but also take pressure off a bullpen that has shouldered a heavy load in high-leverage situations.

For Arizona, the return is substantial and addresses multiple organizational needs. Cole Young is a polished left-handed hitter with advanced plate discipline and a high floor at shortstop, giving the Diamondbacks a potential franchise cornerstone up the middle. Emerson Hancock, despite some injury setbacks, still boasts mid-rotation upside and is ready to contribute at the big-league level. Tyler Locklear provides power and versatility, capable of slotting in at first or third base and offering a long-term solution at a corner spot.

The Diamondbacks’ front office has made it clear they want to remain competitive even as they retool. This deal allows them to do just that, infusing the roster with young, controllable talent while maintaining a competitive core. The Mariners, meanwhile, get the impact starter they desperately need without sacrificing their entire farm system or gutting their big-league roster.

This proposal stands out because it balances risk and reward for both clubs. Seattle parts with significant prospect capital but retains key contributors and avoids dealing from areas of current big-league strength. Arizona, meanwhile, maximizes Gallen’s value at a time when the starting pitching market is thin and demand is high. The Diamondbacks can immediately plug Young and Hancock into their lineup and rotation, keeping the window open for a quick return to contention.

If the Mariners are serious about making a deep playoff run in 2025, Zac Gallen is the perfect target. His blend of experience, upside, and postseason pedigree fills Seattle’s most glaring need and signals to the rest of the league that the Mariners are ready to win now. For Arizona, moving Gallen is a tough but necessary decision that can accelerate their retooling process and set the stage for future success.

As the trade deadline drama unfolds, all eyes will be on Seattle and Arizona. If both sides are willing to make bold moves, this blockbuster could reshape the playoff picture, and perhaps, the future of both franchises.