MLB 26-and-under power rankings: No. 6 Seattle Mariners

By Jordan Shusterman
Updated Mar 20, 2023 11:27 am ET

FOX Sports' 26-and-under power rankings are a new spin on the classic prospect rankings. Yes, prospects are important, but with all the game-changing young talent already in the bigs, farm systems alone can’t tell the whole story. So we’re diving deep into every single MLB club, ranking them all by the players in an organization entering their age-26 season or younger — from the bigs to the farm. Each weekday through March 27, we’ll count down from last to first. 

No. 6. Seattle Mariners
26-and-under total score: 21 (out of 30)

With so much energy and emotion devoted toward their historic postseason drought, it was often difficult to imagine what life would be like for the Seattle Mariners after finally reaching the postseason again. The dramatic Cal Raleigh walk-off homer to send Seattle to October may have been the end of one story, but it was also the beginning of another. 

A common refrain among players is that the hardest part isn’t necessarily reaching the big leagues, it’s staying there. The Mariners now find themselves in a similar situation, having finally gained entry into the prestigious community of postseason contenders but with much work ahead to ensure a lengthy stay among that tier of teams. As long as they share a division with the powerhouse Astros — who rank even higher on these rankings — the Mariners will need a lot to go right to realistically challenge for an AL West crown. However, there is tremendous upside present on this roster on both sides of the ball capable of making that a reality sooner rather than later. 

Big-league position players: 8 (out of 10)

Every once in a while, a generational talent comes along and makes the hardest game in the world look stunningly simple. And yet, for a month, let us not forget Julio Rodríguez struggled badly. He struggled in part because of a shockingly unlucky run of bad strike-three calls, but the numbers were what they were. At the end of April, the eventual AL Rookie of the Year had a .544 OPS. Major League Baseball wasn’t looking particularly easy, but it wasn’t supposed to be — especially for a 21-year-old.

A month was all he needed, though. A month to feel out the league, a month to figure out how to consistently broadcast the J-Rod Show to the local and national audience, a month to learn how to attack the best pitchers on earth. Just a month. 

From May 1 on, only four players were better offensively than J-Rod, and two of them won MVP. If his play and production on the field weren’t enough, Rodríguez also emerged as a charismatic, charming and overwhelmingly likable personality away from it. All of which combines to make him the obvious next face of the franchise for Seattle — if not one of the faces of MLB — and earned him a record-setting contract extension that could keep him in the Pacific Northwest for life. The J-Rod Show is only getting started. 

Raleigh was much more than just his one epic moment — that walk-off homer was one of 27 dingers he launched in 2022, the most of any catcher in baseball. If that came as a surprise even after his rough rookie campaign at the plate, perhaps it shouldn’t have. The switch-hitting Raleigh led all minor-league catchers in home runs with 29 in 2019, and has always boasted plus power, especially from the left side. Most importantly, the man they call "Big Dumper" has already earned a stellar defensive reputation behind the dish, which only makes his slugging prowess that much more of a bonus. 

Finding a franchise catcher is one of the hardest things an organization can do, and Raleigh appears to be exactly that. The batting averages may always be low — though maybe somewhat higher now with the shift going away — but the power and aptitude as a field general combine to make Raleigh one of the best young catchers in the game, not to mention provide one of the best nicknames.

Speaking of the nickname, the person who introduced the world to the "Big Dumper" moniker was actually Raleigh’s friend and teammate, Jarred Kelenic. Unlike Raleigh, who found his major-league footing in 2022, Kelenic has struggled mightily to adjust to big-league pitching to a troubling degree. No matter how you slice it, Kelenic’s .589 OPS in 558 MLB plate appearances has been a massive disappointment thus far. The good news is that at just 23 years old, the tremendously talented and hard-working Kelenic is far from doomed to a lifetime of ugly slash lines. 

He’s attacked his failures head-on and has made adjustments to his swing and setup that have manifested into him being one of the more productive hitters in the Cactus League this spring. The Cactus League is not the American League, but it’s a promising start to a crucial season for the young outfielder. He may never be the co-star in the outfield alongside Rodríguez that many had hoped, but Kelenic looks primed to play an important supporting role in the near future if his adjustments do indeed stick. 

Big-league pitchers: 9 (out of 10)

Seattle boasts one of the strongest quartets of under-27 pitchers in all of MLB: two first-round picks from mid-major schools (Logan Gilbert from Stetson in 2018; George Kirby from Elon in 2019) who have already blossomed into mid-rotation workhorses at worst (and legitimate aces if everything clicks), and two dynamite relievers whisked away from the Padres in trades at the 2020 trade deadline (Andrés Muñoz and Matt Brash). 

Now entering his third big-league season, the large, lanky Gilbert has already established himself as a safe bet to munch innings rather efficiently, but his ceiling remains somewhat in question. His elite extension (how far down the mound he gets when he releases the pitch) makes his already-plus fastball play up even more, but the secondaries lag behind, in turn sapping his ability to consistently garner whiffs out of the zone. That may be nitpicky, and we’re still talking about a 25-year-old who just posted a 3.20 ERA in 32 starts. But Gilbert now suffers for being compared to his new rotation mate in Kirby, who couldn’t have possibly ended the season on a higher note. 

After closing out the AL wild-card series against Toronto in his first career relief appearance, Kirby went seven scoreless with five strikeouts and zero walks against Houston in an iconic and outrageous ALDS Game 3 that ultimately ended Seattle’s season in 18 innings. It was the best any starting pitcher did against the eventual World Series champions at any point during the postseason. Long known for his prodigious strike-throwing, Kirby’s stuff now wows to a similar degree, giving him a rare ace upside that he has already demonstrated on the biggest stage in his very first opportunity. 

Two starters of Gilbert and Kirby’s caliber alone would warrant a sky-high score in this category, but factoring in Muñoz and Brash is what puts Seattle in the absolute top-tier of young big-league pitching across the league. 

Muñoz’s arm talent has never been in doubt, but he was finally healthy enough to unleash his overpowering arsenal on opposing hitters over the course of an entire season. You know your stuff is good when you can touch 103 MPH yet still throw your slider nearly two-thirds of the time. Muñoz's 32.7% K-BB% was second-best among MLB relievers behind only former Mariners flamethrower Edwin Díaz.

Brash was less of a known commodity entering his rookie year, but he finished it with a similar reputation to Muñoz as one of the more unpleasant at-bats in baseball. His slider has already taken on near-mythical status, except it’s very, very real — real to the point that one evaluator argued that its unique metrics make it — and I’m not joking — "maybe the best pitch in terms of pitch movement and velocity in major-league history." A smart person said that! Having seemingly accepted his fate as a dynamic reliever, Brash is set to be a fully operational late-inning weapon for manager Scott Servais. 

Prospect position players: 1 (out of 5)

The 12th overall pick by Seattle in 2021, catcher Harry Ford has gotten far more mainstream attention than most prospects who have yet to play above low-A, thanks to his starring with Team Great Britain during the World Baseball Classic. Ford’s plus speed and overall athleticism stands out at his position, and he’s already demonstrated his raw, plus power on the international stage. Early returns in the minors (.863 OPS in Modesto) are tremendously positive — especially for a demographic (high school catcher) that is one of the riskiest to gamble on high in the draft — but this is a 20-year-old with a long road of development ahead of him on both sides of the ball. 

Ford's future behind the plate is clouded by both his own defensive inconsistencies and Raleigh’s presence as a franchise pillar, but his bat will always be the calling card no matter where he fits on the diamond. 

With Ford a few years away at least, Seattle’s poor grade in this category is rooted primarily in its lack of impact hitters in the upper minors. Outfielder Cade Marlowe is a fantastic development story. A 20th-round senior signee from Division II West Georgia, Marlowe has been one of the most productive hitters in minor-league baseball over the past two seasons, albeit while being old for most of the levels he’s played at. He’ll get a chance to contribute at some point in Seattle in 2023, but he projects more as a useful bench piece than a clear-cut starting outfielder. 

Felnin Celesten (Dominican Republic), Lazaro Montes (Cuba), Michael Arroyo (Colombia), and Gabriel Gonzalez (Venezuela) are all recent high-profile signees out of the international market with varying levels of hype and promise. It’s unrealistic to expect another J-Rod to come around again anytime soon, but this system’s best hope at another future star on the position player side is likely found among that group, as this organization has an excellent recent track record of identifying and developing international talent.  

Prospect pitchers: 3 (out of 5)

This is where the Mariners' player development has really shined in recent years, making it much easier to bet on pitchers in this system maximizing their potential regardless of how many top-100 lists they appear on or what round they were drafted in. 

Consider the breakout of right-hander Bryce Miller, who spent the early part of his collegiate career as an infielder-turned-reliever before making the transition to a starting role during his senior year at Texas A&M. There wasn’t much question that the stuff was real, but little evidence that said stuff would hold up over a starter’s workload in pro ball, especially considering Miller’s relatively unremarkable physical build. 

Such doubts were quashed in emphatic fashion last year as Miller confidently carved across 26 minor-league starts, racking up 163 strikeouts in 133.2 innings. The organization seems committed to continuing to develop him as a starter, making him the likeliest candidate to jump up and seize the fifth starter spot at some point in the next 18 months, or as a critical call-up in case of injury. 

Acquiring Prelander Berroa from the Giants for utility infielder Donovan Walton may prove to be the next remarkable reliever heist on Jerry Dipoto’s lengthy trade resume. Berroa is still slated to remain a starting pitcher in the minors this season, but his ridiculous repertoire and shaky command suggest a much more likely future in relief, albeit one that could impact the Mariners as soon as this season. It smells like Brash all over again. 

Isaiah Campbell, a 2019 second-round pick, is a former starter who has already transitioned to the bullpen and has found ample success, dominating two levels up to Double-A to the tune of a 1.57 ERA in 46 innings with 59 strikeouts. 

Emerson Hancock’s prospect stock has lost some of its luster since he was selected sixth overall in the 2020 draft, but he’s still tracking as a very capable back-end starter that any contender would be thrilled to have as depth. Taylor Dollard projects similarly to Hancock, while Bryan Woo is a starter prospect who boasts significantly higher upside and could make a huge leap in 2023.

Jordan Shusterman is half of @CespedesBBQ and a baseball writer for FOX Sports. He has covered baseball for his entire adult life, most notably for MLB.com, DAZN and The Ringer. He's a Mariners fan living in the Eastern Time Zone, which means he loves a good 10 p.m. first pitch. You can follow him on Twitter @j_shusterman_. 

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