The Rockies announced Monday that Castillo is dealing with right lat tightness and has been shut down from throwing while undergoing treatment for the injury, TheDNVR.com reports.
Castillo received an invitation to big-league spring training, but the lat injury will likely end his longshot bid to win a spot on the Rockies' Opening Day bullpen. The 25-year-old righty split the 2025 campaign between Triple-A Albuquerque and Double-A Hartford, posting a 2.94 ERA and 64:27 K:BB in 52 innings.