3 Mariners prospects who've made themselves untouchable at 2025 trade deadline

As the 2025 MLB trade deadline approaches, the Seattle Mariners find themselves in a familiar position, needing to make a big move to fuel a postseason push. With one of the deepest farm systems in baseball, Seattle has the prospect capital to make a splashy deal.

But even in a scenario where top-end talent could be moved to land an impact MLB piece, there are three names who have cemented themselves as virtually untouchable.

Lazaro Montes' power impact should and early dominance should make him untouchable

Lazaro Montes has evolved from a raw power bat to a potential cornerstone of the Mariners’ future lineup. Once labeled as a typical boom-or-bust corner outfield prospect, Montes has added layers to his game in 2025. Through late June, he’s shown improved plate discipline, and his power has been on constant display throughout his time in Everett and now Modesto, and will again be on display in the 2025 Futures Game.

Montes leads all minor leaguers with 21 home runs. His left-handed power plays in any park, and scouts now project him as a legitimate middle-of-the-order force who could hit 30-plus homers annually. The Mariners simply don’t have another bat like hsm in the system, so Montes should be viewed as a future star who’s too valuable to deal.

Jonny Farmelo's 5-tool potential should make him off limits at the 2025 trade deadline

Jonny Farmelo, meanwhile, has quickly reminded everyone why the Mariners took him in the first round of the 2023 Draft. After tearing his ACL last year, there were natural concerns about how quickly he’d bounce back, but he’s answered those questions emphatically in 2025.

Prior to landing on the IL with a rib injury, Farmelo had shown flashes of all five tools. His sprint speed had looked fully restored, he was taking solid routes in center field, and his bat had come alive with surprising power as seen in his .610 slugging percentage. He profiles as a dynamic center fielder that could be a table setter at the top of a lineup with some serious pop.

His well-rounded skill set, and high ceiling make him one of the prospects you dream on their uber potential, making him someone who should not being touched unless the return is astronomical.

Ryan Sloan has incredible polish and could anchor a Mariners rotation in the near future

Ryan Sloan, the Mariners’ 2024 second-round pick, may be the biggest riser of them all. At just 19 years old, he’s already pitching like a future ace. His fastball sits in the mid-90s, and he’s shown a plus slider and a changeup that displays a lot of maturity.

Perhaps most impressive is his command. For a 19-year-old with an upper-90's fastball, his 2.0 BB/9 in his first season of professional baseball show the type of polish that the Mariners raved about when they gave him a $3 million signing bonus, nearly $1.4 million over his slot value. In an organization that has done a tremendous job developing arms like Logan Gilbert, George Kirby, Bryan Woo, and Bryce Miller, Sloan looks like the next in line to potentially anchor a future rotation. The Mariners are not in the habit of parting with pitchers this polished this early, and there’s a growing belief that Sloan could be be a fairly fast mover due to the physical and mental maturity.

Seattle has the depth to make bold moves at the deadline — but they won’t come at the expense of their foundational pieces. Montes, Farmelo, and Sloan represent not just potential, but the core of the Mariners’ long-term vision. For a franchise trying to thread the needle between winning now and building sustainable success, these three are off-limits.