Crafting a blockbuster Mariners-Red Sox Rafael Devers trade that actually makes sense

What is going on between Rafael Devers and the Boston Red Sox technically does not concern the Seattle Mariners, but it's only natural to wonder if that could change if the three-time All-Star demands a trade.

For anyone who needs to be caught up, there was discord between Devers and the Red Sox as far back as spring training, when he insisted that he continue to play third base even after the signing of Alex Bregman. The Red Sox won that round, but Devers really put his foot down about moving from designated hitter to first base in the wake of Triston Casas' season-ending knee injury:

The drama has not escalated to the point of Devers asking out, and Bob Nightengale of USA Today says that outcome "likely would not be strongly considered until the offseason."

Speculation is nonetheless running rampant, and the Mariners have already been named the No. 1 destination for Devers by Fox Sports. It is a compelling idea, but what would it actually take for Seattle and Boston to come together on a deal?

Getting Rafael Devers from the Red Sox to the Mariners would require a mix of both prospects and money

Let's start by agreeing that, in the abstract if nothing else, the Mariners should want Devers.

Though things have taken a turn for the better in 2025, the Mariners are a long-suffering franchise on the offensive side. This is also a franchise that has famously never appeared in the World Series, yet its window to do so is certainly open. The Mariners have won at least 85 games in each of the last four seasons, and they're in first place in the AL West at 22-17 so far this year.

The 28-year-old Devers has been one of the top hitters in the American League for almost a decade, having recently shrugged off a cold start to this season to raise his OPS to .888 with seven home runs. He even excels at T-Mobile Park, posting a .938 OPS in Seattle for his career.

It's Devers' contract that stands as the biggest hurdle in the way of a potential trade between Seattle and Boston. He is only in Year 2 of a 10-year, $313.5 million deal, though its average annual value works out to about $29 million by way of deferrals from 2034 through 2043.

According to FanGraphs, the Mariners are operating with a payroll that is $12 million north of what they spent in 2024. They've indeed already added money since Opening Day, as they absorbed a couple million dollars' worth of salary when they claimed Leody Taveras from the Texas Rangers.

We're therefore assuming that any deal between the Red Sox and Mariners would need to be cash-neutral or close to it, at least from the perspective of average annual value. Yet we're also assuming that the final deal would need to be more than a bad contract swap or a salary dump, as both sides would surely want some added value on the side.

With this in mind, here's a trade proposal that checks out as a "Fair Deal" at Baseball Trade Values:

• Mariners get: DH Rafael Devers, RHP Richard Fitts, RHP Luis Perales, $48 million cash
• Red Sox get: RHP Luis Castillo, C Harry Ford, 1B Tyler Locklear

This is pretty much the 2021 Nolan Arenado trade between the St. Louis Cardinals and Colorado Rockies, only more complicated.

Because Castillo's five-year, $108 million contract pays $21.5 million per season, there's only about a $7.5 million difference between him and Devers in terms of AAV. The $48 million going from Boston to Seattle wouldn't entirely negate that, and the Mariners would also have to pay Devers a $2 million assignment bonus. Still, let's call it close enough.

As Ford is blocked by Cal Raleigh and Locklear clearly isn't trusted to handle first base, the prospects going to the Red Sox wouldn't necessarily be missed by the Mariners. They would have more certain futures in Boston, where first base is wide-open and there is no long-term answer at catcher.

For Castillo's part, the emergence of Emerson Hancock and the looming returns of Logan Gilbert and George Kirby arguably render the veteran righty expendable. He would be no more an ace in Boston than he is now in Seattle, but the Red Sox frankly need more support for Garrett Crochet in their rotation.

The two arms that would come to Seattle aren't household names, but both carry significant promise. MLB Pipeline has Perales and Fitts ranked as Boston's No. 4 and No. 14 prospects, respectively, with the former getting a 70 grade for his fastball. Admittedly, the Mariners would be buying low on both, as Fitts is coming back from a pectoral strain and Perales had Tommy John surgery last June.

Yet the real prize, of course, would be Devers himself. Jorge Polanco's hot start as the Mariners' primary DH would complicate the fit, but he's also started games at second base and third base this season. And who knows? Maybe Polanco would be willing to move to first base, where the Mariners need to do better than their Rowdy Tellez-Donovan Solano tandem.

It can't be emphasized strongly enough that all we're doing here is playing fantasy baseball. Until Devers actually requests a trade, the safest assumption is that he and the Red Sox will find a way to work through their differences.

"Rafael Devers, Seattle Mariner" is nonetheless an idea worth daydreaming about. With him alongside Julio Rodríguez for rest of 2025 and the foreseeable future, it would perhaps be easier than ever to imagine the Mariners finally getting to the Fall Classic.