3 prospects from MiLB champion Everett AquaSox on a fast track to Mariners

No matter what happens at the big-league level, the Seattle Mariners organization is going to walk away from 2025 with at least one championship.

The Everett AquaSox, Seattle's High-A affiliate, secured the Northwest League title with a 6-3 win over the Eugene Emeralds on Sunday. It's a remarkable outcome, as the prospects the AquaSox lost via promotions to Double-A throughout 2025 include Colt Emerson, Lazaro Montes, Michael Arroyo, and Jurrangelo Cijntje. Per MLB Pipeline, they represent half of the Mariners' eight best prospects.

However, there are still a few members of the 2025 AquaSox who are worth knowing as candidates who could debut in the majors relatively soon, such as 2027.

3 Everett AquaSox who could be on a fast track to the majors

RHP Ryan Sloan

Age: 19
2025 Stats (A/A+): 21 GS, 82.0 IP, 80 H (5 HR), 90 K, 15 BB, 3.73 ERA
MLB Pipeline Rank: MLB No. 41, Mariners No. 5

Sloan has looked like a steal from the moment the Mariners drafted him in the second round back in 2024. Though they had to go over-slot with a $3 million bonus to get him to sign, they still nabbed MLB Pipeline's No. 18 prospect with the No. 55 pick.

Though Sloan's season ended early because of an eye procedure, he still made the biggest leap of any Mariners prospect this year. To wit, he wasn't even in MLB Pipeline's top 100 back on Opening Day.

As Sloan walked only 1.9 batters per nine innings, it's his control that sets him apart from the garden-variety teenaged pitching prospect. Yet the ace-caliber stuff is there, too, as he can run his fastball up to 99 mph with a plus slider and changeup on the side. The latter proved its worth this year by helping him silence left-handed batters with a .647 OPS.

It took just 18 starts for Sloan to make the jump from Single-A to High-A. Though it's hard to imagine him getting all the way to Seattle in 2026, it isn't hard to imagine him getting to Triple-A Tacoma by the end of the year.

SS Felnin Celesten

Age: 20
2025 Stats (A/A+): 104 G, 472 PA, 6 HR, 21 SB, .273 AVG, .345 OBP, .375 SLG
MLB Pipeline Rank: MLB No. 92, Mariners No. 9

We were running "What's wrong with Felnin Celesten?" stories as late as July 3 this year, as he only had a .712 OPS in 57 games with Single-A Modesto through the end of June. A struggle with vertigo-like symptoms didn't make things any easier.

It was in July that Celesten finally got his feet under him and bumped his OPS up to .766 in his last 36 games with Modesto before he got promoted to Everett. He promptly crushed a home run for his first hit at High-A.

Power is not going to be Celesten's thing as a pro, but he has above-average tools otherwise. At worst, he profiles as a useful utility infielder with on-base acumen and speed. If his defense at shortstop continues to look like an asset, he's a potential regular there.

The trick for Celesten, who just turned 20 on Monday, will be to keep up his momentum next year. If he does, he could at least emerge as a desirable trade chip even if the Mariners hand their shortstop keys over to Colt Emerson within the next year or so.

RHP Teddy McGraw

Age: 23
2025 Stats (A/A+): 14 G, 12 GS, 28.1 IP, 32 H (1 HR), 33 K, 8 BB, 3.18 ERA
MLB Pipeline Rank: MLB No. 41, Mariners No. 5

Granted, "Teddy McGraw" and "fast track" have typically not gone together since the Mariners drafted him in the third round in 2023. He was recovering from Tommy John surgery at the time, and further elbow trouble limited him to four outings last year.

Still, McGraw at least avoided surgery this time around. And even if he was only used in short spurts in the Arizona Complex League and with Everett, he was nonetheless more effective in the latter with a 6.0 strikeout-to-walk ratio.

McGraw features a sinking fastball with high-90s velocity, but his best pitch is a slider that gives off Matt Brash vibes.

For anyone hoping McGraw can hack it as a starter, that ship has sailed. Yet he already looks like a future bullpen asset, and he's at an age where the Mariners might be able to make that happen fast if he's able to avoid further arm trouble.