This story was excerpted from Daniel Kramer’s Mariners Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.
SEATTLE -- The next wave of Mariners prospects isn’t just on the way. A few of them already arrived late in 2026.
And how much the youngsters will get a chance to contribute in ‘27 will be a leading storyline heading into Spring Training, which could hinge on how president of baseball operations Jerry Dipoto and general manager Justin Hollander round out the roster.
Here’s a wide-ranging look at the state of Seattle’s farm system, which checked in at No. 9 in MLB Pipeline’s most recent rankings.
COMPLETE MARINERS PROSPECT COVERAGE
3 players who forced their way onto the radar this year
LHP Kade Anderson (No. 1 prospect): He avoided a significant scare when taking a 103.8 mph comebacker off his pitching arm during his final start. And while it did leave him with a bruised finish, the 22-year-old nonetheless was on an upward trajectory heading into the offseason, with a 3.79 ERA (104 ERA+, where league average is 100) over seven starts. By all indications, his promotion on Aug. 22 was a permanent one, and he’ll be eyeing a full MLB workload in 2027.
INF/OF Michael Arroyo (No. 3): He might be the 40-man roster’s most intriguing player heading into winter, given that the club was willing to give him a chance in September (albeit in a strictly platooned role) and that the clearest position for him to contribute is now wide open (with left fielder Randy Arozarena heading to free agency).
OF/DH Lazaro Montes (No. 4): Will the Mariners give the huge slugger runway for a permanent opportunity, after a few epic moments as a September callup? Or will they want to see more seasoning at Triple-A Tacoma? These questions might be answered based on who the Mariners add externally this winter, as well as Montes’ showing in Spring Training.
2 possible breakout players to watch in 2027
SS Felnin Celesten (No. 5): A groin strain that landed him on the injured list in early September ultimately ended his season, and it capped a tough six-week stretch after being promoted to Double-A Arkansas. But up to that point, the extremely athletic shortstop was putting together arguably the best season for a position player in the entire system, with 13 homers and a .943 OPS at High-A Everett that led him to earning Northwest League MVP honors. Unfortunately, health has been a defining factor to his Minors ascent. But if he can stay on the field throughout 2027, the 21-year-old could be that much closer to the MLB conversation.
C Boston Smith (No. 13): Heck, 2026 might’ve actually been his true breakout. But 2027 will be his first full season in the organization. Smith crushed nine homers after arriving from the White Sox organization in the Luis Castillo trade to bring his season total to 31 -- making him one of just 23 Minor Leaguers with at least 30 last season. The Mariners are giving him more runway to continue his hot stretch in the Arizona Fall League.
1 big question for next season
When could Ryan Sloan (No. 2) make his debut?
Sloan could’ve easily headlined both categories above. But because he has arguably the highest upside of any player in the system -- and that he’s inching closer to The Show -- the electric right-hander is in a class of his own.
Sloan racked up a 3.73 ERA over 101 1/3 innings and 22 starts last season, all at Arkansas. That represented a climb from 82 innings the year prior, which could loosely put him in the range of 120-130 for 2027 -- firmly in the range for that Seattle’s front office could feel comfortable allocating a chunk of those in the big leagues.
They haven’t yet said it publicly, but Sloan should report to camp No. 6 on the depth chart, making him the first arm on the outside looking in should the Mariners have a need at any point.