Athletics blockbuster fires warning shot at Mariners, AL West with relocation looming

The Athletics just did the Seattle Mariners a solid by removing one of baseball's best closers from the AL West. But come the A's inaugural season in Las Vegas in 2028, the Mariners and the rest of the division may come to regret it.

For anyone who hasn't yet heard, Mason Miller is on his way with JP Sears to San Diego to join the Padres. Jeff Passan of ESPN was the first to report on a massive deal between the two sides, with four prospects headlining the return for the Athletics.

This is a ridiculous haul from the perspective of the A's. Leo De Vries is ranked by MLB Pipeline as the No. 3 prospect in all of baseball, while Braden Nett, Henry Baez, and Eduardniel Núñez ranked as the No. 3, No. 13, and No. 17 prospects within San Diego's system.

Mariners should be shook by how much the A's loaded up their farm system

The consolation for the Mariners right now goes beyond how they look World Series-ready after adding Eugenio Suárez, Josh Naylor, and Caleb Ferguson. They have somehow kept all eight of their prospects in MLB Pipeline's top 100, meaning they still have a case for the strongest farm system in all of MLB.

But if it's the future you want to talk about, well, that is where you have to hand it to the A's for what they're building.

They have Brent Rooker and Lawrence Butler signed for the long haul after their huge seasons in 2024, and it seems highly possible that the A's will have the top two vote-getters for the AL Rookie of the Year. Despite his fractured forearm, shortstop Jacob Wilson was just an All-Star and is batting .312 overall. Then there's first baseman Nick Kurtz, who has rapidly ascended as one of baseball's top sluggers with a 1.039 OPS and 23 homers in just 70 games.

Now here comes De Vries, at least eventually. The 18-year-old shortstop gets above-average grades across the board, and it speaks volumes that he is having a solid season at High-A (.767 OPS, 8 HR) despite being 4.3 years younger than the average player at that level. The switch-hitter projects as a do-it-all shortstop, with a potential ETA of 2027.

Nett, Baez, and Núñez, meanwhile, offer the long-term pitching upside the A's had badly needed. Nett has already made it to Double-A, where he's put his fastball and slider to work racking up a 3.39 ERA in 17 starts.

In all, it's an impressive infusion of talent for the A's, who aren't even likely to miss Miller and Sears all that much. While Miller is indeed an All-Star closer with a triple-digit fastball, he had shown some volatility earlier this year. And besides, it has never been easier to dig up dominant relievers than right now in this day and age.

As the A's proceed with developing their new prospects, they can otherwise look forward to a whole lot more in the way of resources once they move from Sacramento to Las Vegas. A lot still needs to be done in this regard, but they have broken ground on their new stadium. And even if there didn't seem to be much groundswell locally for getting the A's to Sin City in the first place, the move from Oakland to Las Vegas has sure worked out for the NFL's Raiders.

For the Mariners, it all amounts to another reason to make hay while the sun shines and win right now. Not that they needed it after 48 years without a World Series appearance, of course, but better to make it happen now before the A's start throwing their weight around.