SEATTLE — For years, the identity of the Seattle Mariners has been carved into the mound. Power arms. Precision command. Relentless durability. In 2026, that identity may not just carry them back to October — it could carry them all the way to the top.

And if you ask MLB Network insider Jon Morosi, the pitcher who holds the ultimate key isn’t necessarily the one who dominated last year. It isn’t the innings-eating workhorse. It isn’t even the breakout sensation. It’s the one with the highest ceiling still untapped: George Kirby.

“When he’s really going, when he’s really at his peak … I still think Kirby has the biggest upside,” Morosi said in a recent radio appearance. And in a rotation loaded with All-Stars, that statement lands like a thunderclap.

Consider the embarrassment of riches Seattle boasts. In 2023, Kirby looked every bit the ace, posting a career-best 3.35 ERA while leading Major League Baseball in the fewest walks per nine innings (0.9) and the best strikeout-to-walk ratio (9.05-to-1). His command was surgical. His tempo relentless. Hitters often looked defeated before the at-bat even ended.

Then came 2024, when Logan Gilbert made his own emphatic claim to the throne. A 3.23 ERA. A league-best 0.89 WHIP. A staggering 208 2/3 innings pitched. Two hundred twenty strikeouts. Gilbert didn’t just dominate — he devoured innings, stabilizing the rotation like a metronome.

And in 2025, it was Bryan Woo who ignited the fan base with a historic run of 25 consecutive starts of at least six innings pitched. Fifteen wins. A 2.94 ERA. One hundred ninety-eight strikeouts. For long stretches, Woo was untouchable, the engine behind a Mariners club that fell just one win shy of the World Series.

So who is the ace?

That question has become almost philosophical in Seattle. With four All-Star-level arms, each finishing in the top 10 of Cy Young voting in recent seasons, the title rotates year to year. But Morosi’s argument cuts deeper than last season’s stat line.

“I just think that Kirby, the way that he goes about his craft and the demeanor, the stuff,” Morosi said. “When I look at the body and the delivery, there’s projection and ability to say he’s going to stay healthy and be a durable ace for a long time.”

Projection. Durability. Peak.

Because if there’s one reason Kirby’s 2025 felt unfinished, it was timing.

For the first time in his big-league career, Kirby hit the injured list. Right shoulder inflammation shut him down after just one inning in spring training. He didn’t debut until May 22, nearly two months into the season. The ramp-up was rushed. The rhythm disrupted.

His first two starts were rocky — 11 runs allowed. Doubt crept in. But then, on June 8 against the Angels, Kirby unleashed a reminder. Fourteen strikeouts over seven innings of two-run ball. Dominant. Electric. Vintage.

It looked like a turning point.

Instead, the season became a puzzle. He allowed two or fewer runs in 18 of his 27 starts, including the postseason — a mark of consistency many would envy. Yet he also surrendered four or more runs eight times and six or more runs four times. The volatility was uncharacteristic. His 4.21 ERA and 29 walks were career highs.

Was it rust? Fatigue? Lingering discomfort? The Mariners have publicly framed it as a learning year, a recalibration rather than regression.

And that’s precisely why Morosi believes 2026 could explode.

“If Gilbert and Woo maintain ’25 and then we get the best of Kirby,” Morosi said, “there is not a team in the American League that is better than the Seattle Mariners.”

That’s not hyperbole. It’s a warning.

Because the version of Kirby that posted elite command numbers in 2023 — the one who barely walked hitters and attacked the zone without fear — hasn’t disappeared. He’s 28 years old. He’s entering his prime. His mechanics remain clean. His velocity stable. His arsenal deep enough to neutralize both lefties and righties.

Seattle doesn’t need him to reinvent himself. They need him to reclaim himself.

If he does, the math becomes terrifying for the rest of the league. Gilbert providing length. Woo delivering dominance. Kirby blending precision with power. Add a bullpen that has quietly matured and an offense that gained postseason scars last year, and suddenly the Mariners aren’t just contenders — they’re constructed to outlast.

The American League landscape remains competitive, but rotations win championships. And the Mariners’ rotation, if fully synchronized, could overwhelm any postseason bracket.

The story of 2026 may ultimately hinge on whether George Kirby’s bounce-back is incremental — or transformational.

Morosi is betting on transformational.

And if he’s right, Seattle won’t just be chasing October. They’ll be dictating it.