Castro (shoulder) was activated off the disabled list, and optioned to Triple-A Albuquerque on Wednesday.
Castro last played for the Rockies in an April 17 stint prior to injuring his shoulder and being placed on the DL. He made a rehab appearance with Albuquerque on Monday, and struck out one batter while also giving up a home run. He pitched very well with the Rockies earlier this season, so he figures to be back up with the big club later summer.