Complete list of Mariners players who should be available at 2026 MLB trade deadline

The trade deadline is coming, and all the available information says the Seattle Mariners are on the hunt for a proven relief pitcher and/or a right-handed hitter. And there's no reason they can't fill these needs by August 3.

Provided, of course, that they're willing to pay the right price.

So, we've put on our Jerry Dipoto hat and compiled a list of eight major leaguers and prospects that need to be on the table. There are no randos here. These are players other teams would hypothetically covet, especially in trades that would be potent solutions to Seattle's problems.

The Mariners should dangle these 4 major leaguers in trades

Luis Castillo, RHP

Contract Status: Year 4 of 5-year, $108 million, with 2028 vesting option

It's a secret neither that the Mariners have a starting pitching surplus, nor that Castillo is the obvious odd man out. His $24.15 million salaries are a heavy burden for a mid-market team like the Mariners. And if given truth serum, the brass would probably make no mistake about wanting Kade Anderson in his spot sooner rather than later.

Things have also been a little awkward for Castillo in 2026, so you have to hand it to him for soldiering through and keeping his trade value in a good place. Even if his ace days are over, his 3.67 ERA over his last 11 appearances underscores his potential to help a pitching-needy team elsewhere.

Emerson Hancock, RHP

Contract Status: 1-year, $793,300, free agent after 2030

According to Ken Rosenthal and Will Sammon of The Athletic, the Mariners are telling teams that they're open to trading Hancock. It seems to be a "next man up" thing in the face of an uncertain market for Castillo, and that's fine so long as the Mariners get something they need for Hancock.

Right-handed bats should be in play, and Hancock is on the same tier as guys like Casey Schmitt, Matt Shaw and Spencer Steer. Each would bring positional flexibility and an ability to hit lefties to Seattle.

George Kirby, RHP

Contract Status: 1-year, $6.55 million, free agent after 2028

If it's one of the Mariners' homegrown aces who must go, Kirby should be at the top of the list. He hits that sweet spot as A) an All-Star-caliber starter, B) controllable beyond 2026 and C) likely the hardest of the bunch to sign to an extension.

That said, Kirby is definitely a "Break Glass in Case of Emergency" trade candidate. He should only be sent somewhere if coming back to Seattle is someone like, say, Tarik Skubal, Mason Miller or (by some miracle) Byron Buxton. Otherwise, he needs to stay right where he is.

Luke Raley, RF

Contract Status: 1-year, $2.05 million, free agent after 2028

All eyes are on the rotation surplus, but there's a bit of redundancy between Raley and Dominic Canzone, too. They're both left-handed-hitting, defensively-limited types. One of them can go, especially if it means inserting an everyday right-handed hitter into the resulting hole.

As a guy with a 137 OPS+ and club control through 2029, Canzone has more trade value than Raley. But that's also why he should stay. Even if Raley isn't likely to fetch much on his own, another team could see him as a useful throw-in because of his left-handed power.

The Mariners can't be too protective of these 4 prospects

Lazaro Montes, RF

Mariners Rank: No. 3

Montes got off to a slow start for Double-A Arkansas, but a lot of that had to do with his power getting suppressed by the cavernous Dickey-Stephens Park. He has since turned the power back on, and is now up to 59 total home runs over the last two seasons.

Yet even though we're clearly high on Montes, assessments of him tend to be all over the place. That largely comes down to how he isn't so much a power-first prospect as a power-only prospect, which makes for a volatile projection as a future major leaguer. As such, there's a decent chance that he's never going to have as much trade value as he does right now.

Felnin Celesten, SS

Mariners Rank: No. 4

Celesten is the breakout star of Seattle's farm system in 2026. He's been truly magnificent, batting .313/.407/.528 in 83 games while also playing terrific defense at shortstop. Notably, he earned a ticket from High-A to Double-A in fewer games than even Colt Emerson.

And yet, the fact remains that Celesten sees Emerson at his position when he looks up the Mariners' depth chart. Another fact is that he was in uncertain territory as recently as last year, when he had some health issues and never really got his bat going. Selling high on him could make sense, especially if the Mariners don't want to move him off shortstop.

Michael Arroyo, LF/2B

Mariners Rank: No. 5

Arroyo is on fire, folks. And not just in the sense that he's batting .358 since his promotion to Triple-A. Go back to June 1, and he's batting .346/.420/.564 with a 158 wRC+ in 38 games overall. More broadly, his career minor league OBP is still over .400 in his fifth season.

The trouble with Arroyo is that he's a weird variant of Montes. If Montes is power-over-hit, Arroyo is hit-over-power. And while Arroyo is a better athlete than Montes, he isn't can't-miss defender in left field or at second base. So, like with Montes, it's possible it's only downhill from here with his trade value.

Jonny Farmelo, OF

Mariners Rank: No. 6

Bravo for Famelo, honestly. He went seven picks after Emerson in the 2023 MLB Draft, but then sat out much of 2024 and 2025 because of injuries. Now he's put himself on a fast track in 2026, mostly owing to a red-hot June that earned him a promotion from High-A to Double-A.

In totality, though, it's really only in said red-hot June that Farmelo has looked like the prospect he was meant to be. It's not quite enough to redeem everything else, and it's only natural to worry about a player who arguably already has an "injury-prone" label at 21 years old. If there's a time to sell high, it might be now.

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