The Seattle Mariners’ toughest days this season are probably revolving around Luis Castillo.

After a series of inconsistent performances and growing debate in the Seattle media about his potential move to the bullpen, Castillo finally spoke out—and his response quickly sparked controversy in the MLB community.

“I still believe I’m a starter,” Castillo shared after analyses from experts suggested the Mariners needed to consider changing his role. “I know I’m going through a tough period, but I never thought I was out of the running in rotation.”

That statement came just hours after an analysis from the Seattle media suggested the team “should seriously consider” moving Castillo to the bullpen due to his prolonged slump in form.

Luis Castillo was once the Mariners’ irreplaceable ace.

Since arriving in Seattle in 2022, he has become an icon of rotation, playing a major role in helping the team end a playoff drought that lasted over two decades. But the 2026 season is unfolding in a completely different direction.

MLB experts believe Castillo is no longer maintaining his dominance:

velocity has decreased at many times;

changeups have lost their sharpness;

and his ability to control late innings has become inconsistent.

Some recent statistics show that opponents are heavily exploiting his sinker and fastball shots in the middle zone — something rarely seen during his peak years.
A widely circulated analysis from the Seattle Times even described Castillo’s current form as “not sustainable for rotation.”

The pressure on Seattle now doesn’t just come from Castillo alone.

The Mariners’ rotation is becoming more crowded after the return of Bryce Miller, while young pitchers like Emerson Hancock are beginning to create competitive pressure for positions. This has led many experts to believe Seattle needs to make a difficult decision: continue to put faith in Castillo or change his role before the season spirals out of control.

ESPN insider Jeff Passan has also mentioned the possibility that Castillo is better suited to the bullpen role at this stage, especially since he still performs well in early innings but declines significantly later in the game.
A noteworthy detail analyzed by the American media:
The opponent’s OPS in the first inning was only around .401

but the total OPS for the entire game increased to nearly .850.

This raises the hypothesis that he could become more dangerous if he only threw short innings as a late-game reliever.

However, Castillo doesn’t want to hear any conclusions about his starter career being over.

According to those close to the team, the Dominican pitcher is disappointed that bullpen debates are appearing publicly so early in the season.

“Pitchers like me always want to get the ball in the first inning,” Castillo said. “That’s how I’ve played my whole career.”

Internal Mariners sources indicate Castillo is still training as a regular starter and hasn’t received any official notification about a role change.

However, what makes the situation sensitive is that Seattle doesn’t have much time left to “patiently wait” if the AL West race heats up.

Moving Castillo to the bullpen would be more than just a tactical change.

It could become a symbolic moment marking the Mariners’ entry into a new phase — where current performance is more important than past reputation.

Castillo remains one of the highest-paid pitchers on the roster and was once the franchise’s number one ace. Therefore, any move involving him would have a significant impact on the clubhouse.

Some former MLB pitchers believe that moving to the bullpen isn’t necessarily the end.

They cite examples like Dennis Eckersley and John Smoltz—players who revived their careers by switching roles.

On social media, the Mariners community is divided into two distinct camps.

One side believes the team needs to act decisively before it’s too late.

But the other believes Castillo still deserves more time, especially given his contributions to the franchise.

Many fans recall the historic 2022 playoff run, where Castillo threw some high-stakes games to bring Seattle back to a truly competitive position.

Luis Castillo hasn’t been relegated to the bullpen yet.

But for the first time since he became the iconic face of the Mariners, that question has been raised so openly and seriously.

What makes this story special isn’t just his declining performance—but the fact that Seattle is facing a difficult choice between loyalty to the past and the need to win in the present.

For Castillo, this could be the biggest challenge since joining the Mariners.

As for Seattle, the decision they make in the next few weeks could directly impact their entire 2026 season.