Luis Castillo’s Looking Like a True Ace For the Seattle Mariners

Major League Baseball consists of roughly 10-12 starters who are true aces. Not a No. 1 caliber starter. Not the top pitcher in a team’s rotation. An undisputed ace across the game.

For the majority of Luis Castillo’s career, he has profiled as more of the two formers. A top 20 arm in the sport who was the most dependable starter in the Reds rotation during his time in the Queen City. Yet not quite holding his throne on Mount Olympus with the deGrom’s and Verlander’s of the world.

But since arriving in Seattle, specifically in his last four starts dating back to the 2022 postseason, Castillo suddenly looks like he has another level that is in the midst of being unlocked. One that has the potential to transform him into that solidified ace.

Through two starts in 2023, Castillo has been borderline unhittable. He tossed 11.2 innings against the Guardians and Angels, has yet to surrender a run, allowed three hits and struck out 12. He has thus far posted a WHIP of 0.42, an xERA of 0.90 and a FIP of 1.68.

Viewing Castillo’s 2022 playoffs resume, he spun 7.1 shutout innings in Game One of the AL Wild Card Series in Toronto, which ranks as one of the most prolific starts in the history of the franchise, in a 4-0 win.

Then he tossed seven innings of three-run ball in a loss in Houston during Game Two of the ALDS, keeping Seattle within striking distance throughout the contest. And two of the runs surrendered were on a two-run blast from Yordan Alvarez, despite the offering from Castillo landing well off the outer part of the plate. That result speaks more to Alvarez just being that magnificent as opposed to Castillo failing to execute.

Performances like those are what an ace does.

Where Castillo has made a monumental jump since last season, particularly since settling into the Pacific Northwest, is the eye-popping results he has accrued on his fastball. For the longest time over the course of his career, his most effective pitch (by Baseball Savant’s Run Value) was his changeup. Fast forward to 2022 and the tide turned to his four-seam fastball taking center stage (-18 Run Value), with opponents slugging a miniscule .193 against it.

Through his pair of outings this season, Castillo’s four-seam fastball has not skipped a beat. He has so far produced a Run Value of -3 on that pitch and has yet to give up a single hit against his heater.

Part of the reason for that, is few are putting bat to ball against it. Castillo has posted a K% of just under 54% through two starts, with a Whiff% of 41.5%.

His changeup and sinker have also fared well, throwing up opposing slugging percentages of .100 and .182, respectively. Each currently hold Run Values of -1.

Castillo has generated 30 swings and misses through two starts (17 on the fastball). His 13 on Opening Day edged out Shane Bieber by three, and his 17 whiffs against the Angels was seven greater than Jose Suarez who, much like Bieber, also recorded 10.

Looking beyond the nitty-gritty sabermetrics, another mark of a true ace is their ability to be the “stopper” when a team is tail spinning. To take the ball, overpower their opposition and chalk up a much-needed victory. Felix Hernandez played that role for a decade in Seattle when the team was on a losing streak.

After Castillo’s lights out performance against Cleveland, the Mariners scuffled. They lost four straight, dropping the next three contests to the Guardians and having no answers for Reid Detmers in the first game of the Angels series. Castillo took the ball with his team attempting to find some early season footing, and he helped the club do just that over his 5.2 scoreless innings, combined with the support of an offensive explosion in the 11-2 win.

The Mariners rotation ranked as one of the best in the game entering the year, despite it lacking an unquestioned ace. With Robbie Ray expected to miss over a month with a left flexor strain, the team may need Castillo as much as ever.

But at 30 years old, Castillo is far from peaking. In many ways, he is just getting started. And from recent results, he seems to have much more in the tank that he is well capable of tapping into.