When was the last time the Seattle Mariners had the ace of the AL West?

While Félix Hernández’s heyday is hardly ancient history, the cream of the crop has been reserved for pitchers among the league’s best. In Houston, Justin Verlander, Gerrit Cole, and Zack Greinke. In Texas, Lance Lynn, Mike Minor, and Cole Hamels. In Oakland, Frankie Montas, Chris Bassitt, In Anaheim, Shohei Ohtani and, well, look Ohtani’s real good. Not since 2015 have the M’s had a pitcher in the Top-10 in WAR in the American League, the last year of the King’s reign in earnest.

When was the last time the Seattle Mariners had the ace of the AL West?

While Félix Hernández’s heyday is hardly ancient history, the cream of the crop has been reserved for pitchers among the league’s best. In Houston, Justin Verlander, Gerrit Cole, and Zack Greinke. In Texas, Lance Lynn, Mike Minor, and Cole Hamels. In Oakland, Frankie Montas, Chris Bassitt, In Anaheim, Shohei Ohtani and, well, look Ohtani’s real good. Not since 2015 have the M’s had a pitcher in the Top-10 in WAR in the American League, the last year of the King’s reign in earnest.

Once again, however, a top-of-the-line ace rests at the apex of Seattle’s rotation.

Luis Castillo is that caliber of ace, La Piedra a fitting rock holding together the M’s rotation down the stretch but leading the club into the Divisional Round of the playoffs with a masterpiece immediately categorizable as perhaps the finest start by any Mariners hurler in their admittedly minute 39 games of playoff history.

By game score, Castillo falls just a hair behind Freddy García’s series opening game gem with 6.2 shutout frames in the 2000 ALCS and Randy Johnson’s unreal 8-inning display of excellence in game three of the 1995 ALCS against Cleveland. In Seattle’s long-awaited return to the exhilaration of the MLB playoffs, however, Castillo did everything and more to emphasize why Seattle was willing to exchange multiple well-regarded low-minors prospects for the longtime Cincinnati Reds star.

With the contract extension he signed this past September, however, there’s a very real chance Castillo’s career sees him in Mariners Blue/Northwest Green longer than he’ll have donned the crimson in Ohio. That means the chance for Castillo, at least by track record and which projection system you adhere to, to be the most-feared starter in the AL West. ZiPS sees him as in that very conversation, with the 2nd-highest projected WAR of any starter in the division, though that is a grade confounded by the injury history of Jacob deGrom and the more sparing usage of Ohtani. Castillo is in many ways what the M’s hoped Robbie Ray might be in 2022, an impact ace unlike that which they’d acquired in years past. Prior trade deadlines and offseasons in the Jerry Dipoto era saw Seattle make moves at the margins or middle of the pack, adding quality and dependability like Mike Leake and Marco Gonzales, or more injury-prone gambles like Drew Smyly and Nate Karns that did not make manifest steady contributors.

But going big means at times the reward of big results. Castillo’s improvements and adjustments in 2022 yielded the second-best K-BB% of his career and the best in a full season. He reworked his repertoire, dropping his arm slot to make his four-seamer one of the most devastating in the league while shifting from a changeup-heavy pitcher to a balanced one with a slider and sinker to keep hitters guessing. Castillo is a rarity, an innings-eater at high performance and high dependability. To put the cherry on top, next to no players have joined Seattle amid a playoff race and had the impact Castillo has had. And now he’s a Mariner for the long haul.

His age-30 season will not include a trip to the World Baseball Classic to the disappointment of baseball fans everywhere, including his native Dominican Republic, but spending the time in Arizona easing into spring instead of high-leverage work in Miami will hopefully mean another stellar season in the works in Seattle. His signature look, holding one arm aloft in stoic celebration, has the chance to be replicated across little leagues, pickup games, and high school showdowns for the next half decade. As MLB toys with ways to curtail and reverse the sport’s growth into a bullpen-focused rotation and return it to a game more dominated by high-profile matchups of starting pitchers, Seattle has a rotation full of players capable of shouldering innings each night. While I respect the creativity and adaptability of bullpen adaptation, many fans, myself included, are liable to benefit from a version of baseball where the names on the scorecard do indeed work the lion’s share of the game.

The matchup of personalities, styles, and endurances combined with brilliance that starting pitcher duels can be are compelling narratively as well as analytically. Few teams are as well-situated for steady play from their starting five as Seattle, and that foundation begins with The Rock.