Six Mariners prospects with rising stocks in 2026

For as difficult as this year has been for the Seattle Mariners at the major-league level, the organization continued to have one of the better minor-league systems in baseball.

Despite having a top-end talent like Colt Emerson graduate from prospect status, the Mariners still found themselves in the top 10 of MLB’s farm-system rankings last month. And unlike in past years when most of Seattle’s top farmhands were playing at the lower levels, many of Seattle’s top prospects have reached at least Double-A, including a few who have cracked the majors.

With the minor league seasons finished for all but one of Seattle’s affiliates, here’s a look at six Mariners prospects who rose their stocks with strong years in 2026. All prospect rankings are per MLB Pipeline.

Kade Anderson

Anderson, the No. 3 pick in the 2025 draft, was already one of baseball’s top pitching prospects entering this season. However, likely nobody saw what was coming from the 22 year old during his time with Double-A Arkansas.

Anderson turned in one of the greatest pitching seasons ever at the minor-league level, posting a dazzling 1.06 ERA, 0.64 WHIP and 10-1 record with 135 strikeouts over 93 1/3 innings in 18 starts for the Travelers. He held opponents to one or fewer runs in 12 of his 18 starts, including nine scoreless appearances. His efforts have led to him being rated as the top pitching prospect in baseball by multiple publications.

The southpaw was promoted to the majors on Aug. 22 and has gone 1-1 with a 4.29 ERA and 1.38 WHIP over 21 innings through his first four MLB starts. However, he will maintain prospect status heading into 2027.

Anderson began the year as baseball’s top No. 21 prospect and is now No. 5.

Ryan Sloan

Sloan, a second-rounder in 2024, didn’t have the same sort of season as Anderson at Double-A, but he did put together some solid numbers in the Texas League for a 20 year old, which made him 4 1/2 years younger than the average Double-A player.

The right-hander posted a 3.73 ERA, 1.13 WHIP and 4-4 record with 128 strikeouts to 16 walks over 101 1/3 innings in 22 starts with the Travelers. He had three starts of at least six innings with one or fewer runs allowed and twice struck out a career-high 11 batters.

Sloan has moved from the No. 33 prospect in baseball to No. 8. He’s the third-ranked pitcher by Anderson and Pittsburgh’s Seth Hernandez.

Michael Arroyo

The 21-year-old Arroyo continued to show his plus hit tool in the minors this year, leading to his promotion to the majors on Sept. 6.

Arroyo slashed .283/.359/.471 with 18 homers, 23 doubles and five triples in 114 games across Double-A and High-A this year. And while he did see a year-over-year decrease in walk rate (down to 8.1% from 12.4% last year), he also saw a small dip in his strikeout rate (down to 16.4% from 18.7%).

The strong season helped Arroyo move from baseball’s 67th-ranked prospect to No. 44, which included leaping good friend Lazaro Montes to become the Mariners’ third-ranked prospect.

Felnin Celesten

After falling in prospect rankings in previous years, Celesten enjoyed a breakout year that shot him right back up many lists.

Despite struggles at the plate after a July 20 promotion to Double-A, the switch-hitting shortstop slashed .273/.363/.458 with 16 homers, 24 doubles, four triples, 25 stolen bases, 54 walks and 120 strikeouts in 111 games across High-A and Double-A. One of the biggest different for the 20 year old was improved power, as he hit 10 more homers and 16 more extra-base hits than a season ago. Celesten, who had a 25-game hitting streak in High-A, also cut down on his mistakes in the field, going from 29 errors last year to 24 this year while playing 157 2/3 more innings in the field.

Celesten had fallen out of MLB Pipeline’s top 100 prospects entering this year, but he’s now back up to No. 49. He’s also made the jump from No. 7 to No. 4 in the Mariners’ system.

Mason Peters

Peters, a fourth-round pick in 2025, dominated the Single-A level before a promotion to High-A in his first pro season.

The 22-year-old left-hander had a 1.43 ERA and 0.85 WHIP with 68 strikeouts to 12 walks in 14 starts with Single-A Inland Empire before joining High-A Everett. For the full season, Peters had a 2.10 ERA and 0.95 WHIP with 87 strikeouts and 19 walks over 64 1/3 innings in 18 starts.

The Dallas Baptist product made the jump from No. 15 in the M’s farm system to No. 11.

Colton Shaw

The 23-year-old Shaw made the biggest jump into the Mariners’ top 30 prospects among players who weren’t on the initial list or drafted this year, going from unranked to No. 20.

A seventh-round pick out of Yale in 2025, the right-hander had a 4.43 ERA and 1.15 WHIP with 121 strikeouts to 19 walks over 111 2/3 innings in 23 outings (22 starts) with High-A Everett.

Shaw was a two-way player in his first two seasons at Yale and didn’t begin to solely focus on pitching until 2024.

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