Mariners Prospect Update: Ryan Sloan Shoves, Boston Smith Keeps Mashing and Felnin Celesten Takes His Lumps

Sloan is dealing, Smith is launching and Celesten is learning what Double-A demands.

Feb 19, 2026; Peoria, AZ, USA; Seattle Mariners pitcher Ryan Sloan (97) during spring training photo day in Peoria, AZ. Mandatory Credit: Jayne Kamin-Oncea-Imagn Images | IMAGN IMAGES via Reuters Connect

One Saturday night in the minors told us more than a month of prospect rankings. The Mariners’ latest offered a clean look at development in motion: Ryan Sloan overpowered Tulsa, Boston Smith drove in five runs and Felnin Celesten has found a speed bump to work through.

Ryan Sloan Keeps Missing Bats at Double-A

Sloan carved through Tulsa for 5 2/3 innings, allowing one run on five hits while walking one and striking out nine. After carrying an inflated ERA through the first half, he’s really settled in. Sloan has lowered it to 3.75 with 100 strikeouts over 81 2/3 innings. Saturday’s performance also gave him a much-needed response to his previous start, when the Amarillo Sod Poodles tagged him for five earned runs in four innings. 

He’s really become one of the most important arms in Seattle’s system not named Kade Anderson. The fastball/changeup combination has become a legitimate threat week over week. We know the M’s have a habit of developing strong young pitching. Sloan is just another part of that story.

Boston Smith’s Power Surge Continues in Arkansas

Smith went 2-for-5 with a double, a grand slam and five RBI on Aug. 15. That gives him six homers and 14 RBI through his first 10 games with Double-A Arkansas.

Boston Smith crushes a 2-out GRAND SLAM! pic.twitter.com/kRYFnkPRbb

— Mariners Minors (@MiLBMariners) August 16, 2026

The catcher/outfielder is now slashing .289/.442/.615 with 28 home runs and 72 RBI across four levels between the White Sox and Mariners organizations. His run-scoring double and latest home run were simply the newest entries in a season-long demolition job.

Smith arrived from Chicago in the Luis Castillo trade, and he has wasted no time becoming more than a throw-in prospect in the return. He does have a strikeout problem, but the .442 OBP says a lot about his patience at the plate. The Mariners found a player with power, patience and defensive flexibility, then dropped him into a system that badly needed another impact bat.

Felnin Celesten Works Through His Double-A Adjustment

Celesten collected his 114th hit of the season, leaving him one shy of tying his career high. He also stole a base, reminding us of the tools he’s bringing to his new home in Double-A. Unfortunately, the results haven’t been as glamorous.

Celesten is batting .205/.290/.349 with three home runs, 11 RBI and five steals for Arkansas. It’s the 30 strikeouts in 93 plate appearances that stand out the most. It’s entirely too much swing-and-miss. There’s also no reason to panic.

Celesten had seen enough High-A pitching. Another month of beating up that level wouldn’t have accomplished anything. Double-A is supposed to expose weaknesses. Now we get to see whether one of Seattle’s most talented prospects can adjust.