Santos will not be ready for Opening Day after an MRI revealed a mild right lat strain, Shannon Drayer of Seattle Sports 710 AM reports.
Santos had been slated for a bullpen session Monday, but that was scratched after he felt a pinch in his lat area. Testing has revealed a minor strain, and he will presumably be shut down from throwing for a while. Santos is slated to serve in a setup role once he's healthy, but he now joins Matt Brash (elbow) on the shelf for the time being.