Wrapping up the season with the second worst record in the California League, it was a tough year to be a 66ers fan. In their first year in the Mariner organization and needing to replace the dominant Modesto Nuts affiliate, the 66ers shortcomings were largely caused by factors out of their control; with the Mariners drafting heavily from the college ranks in the 2025 draft, many of the typical contributors one would expect to fortify the A-ball roster bypassed the level entirely and made their way
to Everett to start the year. Despite the struggles in the win column for much of the year, this team still had a ton of strong performers that made the season incredibly exciting (particularly in the second half), and many of the system’s top 20 prospects appeared on this roster at some point in time this past year. Led by a strong pitching staff all season, the Mariner’s A-ball affiliate kicks off LL’s series of minor league “year in review” that we’ll have for you in the upcoming weeks.
Team Performance
First Half Record: 28-38 (-52 Run Differential)
Second Half Record: 31-34 (+39 Run Differential)
Final Record: 59-72
Team ERA: 5.04 (second in Cal League)
Team OPS: .755 (seventh in Cal League)
Stat to Know: Led California League in K/BB ratio (2.80)
Season Stars
Mason Peters
Easily the biggest riser of any Mariner prospect over the course of the 2026 season, Peters had a sensational first season as a professional and dominated his way through the Cal League. With as impressive a resume as any arm at the level, Peters posted 50.1 IP at the level and recorded 68 punchouts to just 12 walks, dominating his way to a 1.43 ERA and earning a promotion up to Everett late in the summer. Peters is an undersized pitcher with a slight frame and does not overwhelm with velocity, but his innate ability to spin the baseball and immense feel for his fastball-breaker combination make him one of the most exciting prospects in the entire system. He’s still a ways behind system-leading hurler Ryan Sloan, but he’s got a rather strong argument for the second best arm in the organization’s minor league ranks and should be primed for a strong 2027 season at High-A.
Ace Reese
One of, if not the strongest performer of anyone drafted in the entirety of the 2026 MLB draft, Ace Reese made it clear he had little to prove at the A-ball level, making mincemeat of opposing pitchers and smashing his way to an OPS of nearly 1.200. A line of .440/.530/.667 is obviously impossible to ignore, and even though Reese arguably would have been more appropriately placed in High-A or even Double-A, his dominance is quite assuring of his acumen at the plate. The defense at third base (a position he’s still rather new to) left a lot to be desired, and he’ll have to put in a substantial amount of work if he wants to dispel the 1B/COF archetype many have already lumped him into, but regardless of where he ends up, Reese is going to hit, and he’s going to hit a lot.
Korbyn Dickerson
The first-half hero of the lineup, Dickerson was routinely putting in work for this 66ers lineup in its darkest of times. Dickerson, a fifth rounder in 2025, manned center for IE defensively and showed off a compelling combination of power and speed that has him amongst the better bats in this system. Logging 35 steals (21 for IE) and 15 homers (9 for IE) on the year, Dickerson’s premium glove up the middle and tantalizing raw tools at the plate make him a must follow for the 2027 season; he’s struggled a bit with the bat-to-ball, but he started showing improvement after his promotion to Everett and was a key player for IE for much of the season. Given the wave of major league promotions that many of the top prospects in this system earned this season, don’t be surprised if Dickerson sneaks his way on to top ten prospect lists this offseason. He’s a really good player that’s got a bright future ahead of him.
Sleepers
Hayden Yost
Arguably the biggest breakout of the 2026 draft class thus far, Yost, a fifth round outfielder from the University of Florida, absolutely raked in his limited sample of professional baseball and looks like a potential steal as a mid round gem. The lefty slugged his way to a .999 OPS across 114 PA’s and showed off a blend of power and bat-to-ball that’s hard to teach. He’s able to maximize his thump with a good feel to pull the ball in the air, and his clear command of the zone and his barrel bode incredibly well for his future as he moves up the minor league ranks. He was a huge part of the second half resurgence for this roster and should be on his way to Everett next season.
Jackson Steensma
If it weren’t for some midseason injuries that derailed his outstanding start to the season, we may be talking about Steensma as one of the stars of this entire pitching staff. Steensma, who worked 43.1 innings of 4.57 ERA ball this season, looked like a far more superior pitcher for much of the first half. There was clearly something off with him after returning from a multi-month hiatus in July as his performance took a bit of a hit, but his ability to rack up K’s while limiting walks is incredibly intriguing regardless of his late season struggles. He’s physical, has good stuff, and looks like he could be a very intriguing arm; health permitting, he’s one of the better pitchers in this system.
Anderson Guevara
Maybe the deepest cut on this list, Guevara is a fun reliever pick that has some nasty stuff on the mound. Guevara’s K rates sit just under 38% for the year and though he can get wild at times, his diabolical slider is a true whiff-getter, and there’s enough bat missing potential to dream of a successful career as a reliever. He’s a name to know for the true prospect heads that can’t get enough of everything Mariners.
