Seattle Mariners Top Prospects To Know

You are reading the free version of the Seattle Mariners Top Prospects. In this version, you will get the full writeups on the top prospect in the system, the biggest sleeper, and a player I could see breaking out in 2025.

In this edition, you will see what I offer in the full team reports. For every farm system, you will get my top 50 ranked players and detailed reports on the top 30. Each report includes advanced player data, traditional scouting thoughts from live and video looks, plus thoughts from scouts around the league.

Let’s dive in on what you get in the full report!

Glossary:

FFG = Future Fantasy Grade - essentially, what is the likely long-term outcome for the prospect? This is always going to be more conservative. Handing out ace tags is not something I like to do. So, this is a realistic outcome.

90th Peak = If the player hits their best-case outcome, what does it look like?

Variance = How risky is this player’s profile, and how likely are they to hit their likely outcome? Low variance is good; high means more risky.

Format for report: Name/Position/Age on 2025 Opening Day/Height/Weight/Highest Level

Seattle Mariners Top Prospect

1. Colt Emerson, SS, 19, 6’0”/195, A+

No player increased their stock among prospect circles more than Colt Emerson after being drafted in 2023. The Mariners first-round pick slashed .374/.496/.550 with two home runs and ten doubles in 114 plate appearances. Emerson was only 17 years old on draft day, but over the last year, he really added to his 6’1”/200 lb frame.

The 2024 season did not go as planned, as Emerson suffered an oblique injury in April and fractured his left foot when he returned in May. Emerson played just 70 games in the regular season, slashing .263/.393/.376 with four home runs and 22 extra-base hits.

The underlying data was impressive once again as Emerson made contact on north of 82 percent of swings overall and 87 percent in-zone. He rarely chased out of the zone, having a mark south of 20 percent, which led to a 15 percent walk rate.

The exit velocity data did take a step back as Emerson posted just a 102 mph 90th percentile exit velocity after having a 105 mph mark in the small sample in 2023. The average exit velocity checked in around 89 mph. In the Arizona Fall League, Emerson hit the cover off the ball, though, having a near 108 mph 90th percentile exit velocity.

Emerson has seen his run times tick up, and he was 15 of 17 on stolen base attempts. His 6.7-second 60-yard dash suggests plus speed. Ground ball rates are an issue, as Emerson has posted marks around 50 percent his entire career. Failure to lift the ball more will lead to lower home run outputs than the exit velocities suggest.

Currently, he is a line drive machine that hits the ball to all fields. Emerson could be a plus hitter with above-average or better power and speed if all clicks.

FFG: Power/Speed MI

90th Percentile Peak Outcome: .285/.360/25 HR/20 SB

Variance: High

Buy/Sell: Buy

Seattle Mariners Sleeper Prospect

13. Tyler Gough, RHP, 21, 6’2”/205, A

Gough was drafted in the ninth round of the 2022 MLB Draft and after making his pro debut in Single-A in 2023, returned there in 2024 for the entire season. Gough posted a 4.28 ERA across 96.2 innings of work with a 24 percent strikeout rate to an 11.5 percent walk rate.

Having a strong frame, Gough still has some projection, which could lead to more velocity over time. Gough’s fastball sits in the 91-93 mph range, but his ability to spin it and create ride helps it play up. He throws a quite aesthetically pleasing changeup, with a late parachuting shape. It dies in the air and falls off the map. It looks like a plus offering, sitting in the low 80s.

Gough throws a hammer curveball that sometimes plays more like a 12-6 shape and others with more horizontal movement. The pitch sits in the upper 70s and compliments his sweeper in the low 80s that he occasionally throws.

Though the walk rates were a bit high, Gough threw strikes at an above-average rate for his league and age. There is still room for his command to improve, but Gough looks like a prospect who could break out in 2025 if he takes another step forward.

FFG: High Floor SP

90th Peak: 150 IP/4.00 ERA/135 K

Variance: Medium

Buy/Sell: Buy in Deep Leagues

Seattle Mariners 2025 Breakout Prospect

17. Josh Caron, C, 21, 6’0”/215, A

Caron was one of the younger college players drafted in the 2024 class, not turning 21 until August 3. He put together an impressive career at Nebraska but took off in 2024, hitting 16 home runs and having 32 extra-base hits in 60 games. Caron put up a slash of .308/.388/.579 while striking out 19 percent of the time.

The underlying data pops for Caron, who had a 110 mph 90th percentile exit velocity and a 114.5 mph max. For reference, those numbers stack up very similarly to Cam Smith of the Cubs and not far behind Nick Kurtz.

Caron shows a solid approach, chasing around 24 percent of the time out of the zone while making contact on pitches in the zone at an impressive 86 percent clip.

Stepping into pro ball for 13 games, Caron looked quite solid with Modesto. He could start in High-A next season and will be 21 years old nearly all year. He is a bat-over-glove catcher, but the bat is quite strong.

FFG: Power Hitting C

90th Percentile Peak Outcome: .275/.350/24 HR/3 SB

Variance: High

Buy/Sell: Buy