Mariners Option Right-Hander Blas Castaño to Triple-A Tacoma
Castaño's spring ERA of 9.00 over five Cactus League outings sealed his ticket back to Tacoma, where he'll start — but a big-league return could come in relief.
Blas Castaño's spring numbers made the decision straightforward. The Seattle Mariners optioned the 27-year-old right-hander to Triple-A Tacoma on March 11, capping a Cactus League stretch in which he allowed five runs across five innings in five outings, posting an equal 3:3 strikeout-to-walk ratio that offered little argument for a roster spot.
Castaño is expected to begin the 2026 season in Tacoma's starting rotation. The more telling detail, though, is what happens if Seattle comes calling again: the organization views any potential big-league role for him as a reliever rather than a starter, a shift in projection that reflects both his spring performance and his brief, uneven MLB track record.
His lone major league appearance came May 28, 2025, five days after the Mariners recalled him from Tacoma on May 23. He allowed three earned runs on three hits and two walks across three innings of relief before being optioned back to the Rainiers the following day, with Casey Lawrence selected from Triple-A to fill the vacancy. The debut produced a 9.00 ERA in 3.0 innings, matching the single-game line that now sits in his 2025 MLB statistical record.
The 2025 Triple-A season told a more complicated story. Over 29 games with Tacoma, Castaño finished 8-6 with a 5.19 ERA across 126.2 innings, striking out 97 while carrying a 1.39 WHIP. The Mariners recalled him again September 29 as rosters expanded, though the club activated him off the roster on October 21 to close the year.
His path to Seattle's system began in August 2023, when the Mariners signed him as a minor league free agent after the Somerset Patriots released him on August 8. He was assigned to Double-A Arkansas before moving up to Tacoma in June 2024. By November 2024, Seattle had selected his contract from the Rainiers, positioning him for a legitimate shot at the Opening Day roster heading into 2025 spring training. That door closed on March 7, 2025, when he was optioned to Tacoma before the season began, a pattern that has now repeated in 2026.
Across 141 minor league appearances, Castaño carries a 32-41 record with a 4.47 ERA in 589.2 innings, with 509 strikeouts and a 1.37 WHIP. The career numbers suggest durability and volume, but the Seattle organization's current read on his big-league ceiling points toward a bullpen role rather than the rotation he'll be working in at Cheney Stadium to open the year.
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