Much ado has been made about Luis Castillo the last couple years. Each offseason, you hear the calls from fans and media to dump his salary because he isn’t worth it anymore. The Mariners have made it clear that none of their starting pitchers are being traded, but that hasn’t silenced the critics. It’s true that he isn’t the same pitcher he was when the Mariners acquired him. His fastball velo is declining, he’s had more blow up starts, and his secondary offerings aren’t as effective. The 2022 version of Luis Castillo was a #1 starter, a true monster on the mound who dialed it up to 100mph in the playoffs and posted zeros on the scoreboard more often than not. The version we’ve seen in the last couple seasons has not been at that level, and considering the 5-Year, $108 million extension he signed in 2022, that understandably leaves a lot of people unsatisfied. But the death of Luis Castillo has been greatly exaggerated, and some of the criticism he has received has been undeserved, especially given the hurdles he has overcome along the way.
While we Mariners fans lamented his fall from grace, “La Piedra” remained one of the most valuable pitchers in baseball. According to Fangraphs, over the last two seasons, Castillo ranks 21st in WAR amongst all qualified starting pitchers in the MLB, 14th in ERA, 17th in FIP, and 12th in innings pitched. He may not be in the ace conversation anymore, but there’s still fewer than 25 pitchers who have been better over the last two seasons. His ability to post every day has been outstanding and is a huge reason why the 2025 Mariners were able to withstand losing George Kirby, Logan Gilbert, and Bryce Miller for large chunks of the season. Since his breakout season in 2019, he has the 3rd most innings pitched out of all qualified pitchers in MLB.
And this is all while battling constant elbow issues. When it came out in 2022 that his extension with the Mariners included an injury clause that would give them a team option in 2028 if Castillo missed more than 130 days with a UCL repair, the rumors started swirling. It’s been sort of an open secret ever since then, and is certainly still an issue to this day. In an interview with Seattle Sports’ Brock and Salk show on April 29, 2025, ESPN MLB Insider Jeff Passan marveled at how Luis Castillo has been able to be so effective and throw so many innings despite being “a guy whose elbow has been a mess for years”.
Yes, there certainly has been and will be reason for concern when it comes to Luis’s future production. But the track record is there that he can overcome it all and still produce as a workhorse in this rotation. Despite losing velo on his four-seam, he has continued to use it more often and still have success. It generated a +12 run value each of the last two seasons, and opposing batters are hitting just .200 against it. His arm slot has dropped slightly, down from 18 degrees in 2023 to 15 degrees in 2024 and 2025. This provides a bit of an advantage by making his delivery more unique, especially when combined with his bottom 1% extension. The other main reason for optimism is that he had the lowest walk rate of his career last season, and limiting walks is a quality all good aging pitchers have. He has also started to adapt to the decline in his stuff by adjusting his pitch usage and pounding the zone more often while allowing less contact in the zone. I suspect this change is due to improved pitch sequencing & tunneling and staying out of the middle of the plate. This is backed up by the fact that his meatball% (pitches that are middle-middle) dropped nearly a full percentage point in 2025. When you’re throwing thousands of pitches, one percent fewer mistakes matters a lot more than you think.
In simple terms, he’s starting to pitch like a true veteran. And this is exactly what you want to see from an aging pitcher. Nearly every pitcher goes through these same challenges as they age. Velo often declines in a player’s 30’s. But that doesn’t mean their careers are over. Some pitchers adapt, and continue to be effective as they age, like Nathan Eovaldi, who saw his velo decline from over 97MPH to 94MPH in his 30’s. Others, as we saw with Felix Hernandez, struggle to find their way without the overpowering stuff they once relied on.
Castillo’s critics would argue that his underlying metrics don’t look good, and point to his home/road splits as extra reason for concern. He gave up more hard contact last season and struck out fewer batters than before. And it’s true, there isn’t much red on his Baseball Savant Page. But that can be a bit misleading.