Josh Naylor's Mariners Contract Could Vindicate D-backs Trade

Josh Naylor's recent deal might make the Arizona Diamondbacks look smart or foolish.

Oct 19, 2025; Toronto, Ontario, CAN; Seattle Mariners first baseman Josh Naylor (12) reacts after hitting a home run in the sixth inning against the Toronto Blue Jays during game six of the ALCS round for the 2025 MLB playoffs at Rogers Centre. Mandatory Credit: Nick Turchiaro-Imagn Images | Nick Turchiaro-Imagn Images

On Sunday, it was announced that the Seattle Mariners had signed former Arizona Diamondbacks first baseman Josh Naylor to a five-year contract, solidifying his future in Seattle after the D-backs traded him mid-season.

The details of the contract surfaced on Monday — Naylor will receive $92.5 million over those five years, for an average per-year value of $18.5 million.

Naylor had a very successful walk year in 2025. He played well for the D-backs pre-trade, then seemed to hit another gear with the Mariners, helping them push for their first-ever pennant (and falling one game short of that endeavor).

It's hard to call the deal an overpay, and it certainly doesn't look poor for the Mariners, but a deal of that length and magnitude could very well vindicate D-backs GM Mike Hazen on the decision to part with Naylor when he did.

Here's why:

Arizona Diamondbacks May be Vindicated on Josh Naylor

Oct 19, 2025; Toronto, Ontario, CAN; Seattle Mariners first baseman Josh Naylor (12) talks with third baseman Eugenio Suarez (28) in the dugout before game six against the Toronto Blue Jays in the ALCS round for the 2025 MLB playoffs at Rogers Centre. Mandatory Credit: John E. Sokolowski-Imagn Images | John E. Sokolowski-Imagn Images

Prior to the 2025 Trade Deadline, the D-backs sent Naylor to Seattle in exchange for left-hand reliever Brandyn Garcia and minor league righty Ashton Izzi.

At season's end, it looked as if there was potential for it to be a mutually beneficial trade. Garcia showed signs of growth into a leverage role, while Naylor provided the spark the Mariners needed.

Related Content: Exciting Reliever's Development Could be Massive For D-backs

This deal, however, proves that Arizona would have likely had to part with Naylor this offseason anyway. While $18.5 million per year is not a bank-breaking deal, it will take Naylor through his age-33 season after he posted the second-best numbers of his career.

There's risk in paying a player nearing 30 for that long of a contract, and with Naylor's relatively lacking defense (-6 Defensive Runs Saved with Arizona) it would have been difficult to imagine the D-backs committing that much of their reduced payroll to Naylor.

If Garcia continues to trend upward, it's easy to see a benefit to pulling the trigger on the deal. So while the contract may benefit Seattle, the D-backs were able to get some value for their trade asset before he inevitably departed in free agency.

This is not to say Naylor won't reward the Mariners for their investment, but an extension for the stoic slugger was not a likely outcome if he remained in Arizona. And there's nothing that suggests the D-backs would have made the playoffs as a result of hanging onto Naylor.

There's plenty of time for this deal to age well or poorly. Naylor was undeniably a very impactful bat for both the D-backs and Mariners, slashing .295/.353/.462 on the season and .299/.341/.490 for Seattle, with 20 total homers and 3.1 average WAR.

He did, however, showcase some concerns offensively, with a 37.1% chase rate and mostly below-average contact metrics. Inching closer to 30 with each day, there's some risk involved.

There's also a chance the D-backs look like the foolish ones, depending on the state of Arizona's first base position. With no clear-cut option, Arizona may have to take a flyer on a platoon bat, or roll out the Pavin Smith-Tyler Locklear duo that struggled to produce in 2025.

For further discussion on this deal be sure to check out the Snakes Territory Podcast for Jack Sommers and Jesse Friedman's takes on the signing