The Seattle Mariners find themselves in a familiar yet precarious position: stuck in the middle of a tightly contested AL West race where no team has managed to pull away. At 18-20, they trail the division-leading Texas Rangers by just one game, but hovering around .500 is not where they expected to be after last season's promise.
Several key contributors have underperformed, with catcher Cal Raleigh among those struggling to find their rhythm. However, the most critical piece that needs to turn things around is not a bat in the lineup—it's the arm on the mound every fifth day.
Luis Castillo, the 33-year-old right-hander who was a reliable force last season with an 11-8 record, has hit a rough patch to start 2026. Through seven starts, he's 0-3 with a bloated 6.29 ERA—a stark contrast from the ace-like presence the Mariners counted on a year ago. ESPN's Bradford Doolittle recently highlighted Castillo as the one Mariner who needs to change course for the team to have any shot at returning to the postseason.
The numbers paint an even more concerning picture. According to Baseball Savant, Castillo ranks near the bottom of Major League Baseball in several key metrics. His expected batting average against sits at a staggering .304, placing him in the bottom 6% of the league. Meanwhile, the average exit velocity on balls put in play off his pitches is 92.2 MPH—good for the bottom 5% in MLB. Those are not the kind of stats you want from a pitcher expected to anchor a rotation.
The irony is that Seattle's starting rotation has otherwise been steady, with the other four starters posting respectable numbers. But every fifth day, when Castillo takes the mound, the Mariners hold their breath. That inconsistency is a luxury they cannot afford in a division where every game matters.
If Castillo cannot find his form quickly, the Mariners may be forced to look for another back-end starter before June arrives. For a team with postseason aspirations, that's not the kind of shopping list they had in mind. The clock is ticking in Seattle, and all eyes are on their struggling ace to make the break this tight-knit division desperately needs.