Castillo appears to be making good progress in his recovery from a hamstring strain, and the Mariners remain cautiously optimistic that he'll be activated from the 15-day injured list when first eligible Monday,
MLB.com reports. "Progressing as he should be," manager Dan Wilson said. "I don't think there's any expected date, right now, of his return, but progressing as he has. I know Luis is very diligent about getting his work in and trying to get healthy, and I think as far as we know right now, he's doing well."