Mariners Rumors: Seattle is in horrible no-win situation with Luis Castillo trade chatter

The 2025 season is underway and the Seattle Mariners have momentum after a 5-1 week that ended with an emphatic sweep of the AL West-leading Texas Rangers. They're back to .500 at 8-8.

Yet while one might think this would put a stop to Luis Castillo trade rumors, one would be wrong. They're becoming a bit like the Mariners' personal slasher villain, always rising from the dead just when you think they're finally gone for good.

The latest comes from Bob Nightengale of USA Today, who reported Sunday that a team offered the Mariners "a young infielder" in exchange for Castillo. That team was apparently told by Seattle that the three-time All-Star right-hander remains unavailable..."at least for now," in Nightengale's words.

It is not coincidental that this report is coming out now, with the Mariners still reeling from the losses of Victor Robles and Ryan Bliss to injuries that will keep them out months on end. And yet, it should go without saying that the Mariners need to proceed with caution here.

The Mariners arguably should trade Luis Castillo, but the risk to their clubhouse culture would be too great

Here's the tricky thing about the Mariners trading Castillo: There's a solid argument that it's something they should do.

He's a decorated ace who's given the Mariners a 3.38 ERA in 77 starts, but he's also 32 years old and continuing to show signs of decline in his velocity, whiff, and strikeout numbers. To wit, his average fastball has progressed like so during his time in Seattle:

• 2022: 97.4 mph
• 2023: 96.3 mph
• 2024: 95.6 mph
• 2025: 94.6 mph

This is quite the drop, and it is meaningful. Whereas "La Piedra" was in the 92nd percentile with his fastball velo in 2022, he's currently only in the 58th this season.

His whiff rate has likewise gone from the 67th to the 40th percentile in this same window, with his strikeout percentage going from the 76th to the 47th. He has fewer strikeouts this season (15) than he does innings pitched (17.0), which isn't befitting of a modern ace.

There's also Castillo's contract to consider. He's the highest-paid player on the Mariners at $24.15 million, and he'll make that same sum in 2026 and 2027. In theory, that money would be better used on free-agent upgrades or contract extensions (i.e., Logan Gilbert) after this season.

And yet, it is precisely because of Castillo's declining skills and ample contract that we can't say with any certainty that a trade would be worth it for the Mariners.

Baseball Trade Values estimates Castillo's surplus value at just $7.4 million. It's not nothing, but it isn't worthy of either a capable everyday major leaguer or even a top prospect. That kind of value gets you more of a role player, and the Mariners don't need more of those.

And even if the Mariners could find a team that was willing to overpay for Castillo, would president of baseball operations Jerry Dipoto really risk yet another unpopular midseason trade?

Remember the clubhouse-level reactions to his trade of Kendall Graveman in 2021 and of Paul Sewald in 2023? Of course you do, because it wasn't pretty either time. There was talk of betrayal after the Graveman trade, and Cal Raleigh was especially unhappy about the Sewald trade.

If trading a couple relievers in the middle of a season could result in that kind of condemnation, just imagine what would happen if Castillo was shipped off. He's an institution in the Mariners clubhouse, with stories of him being a good teammate seemingly coming out every day.

If you're going to trade a guy like that, it has to be during the winter. Do it during the season, and you risk destroying the team's psyche. Do it during the season and for a modest return, and you risk destroying whatever hope the team has.