Castro was called up Tuesday, Patrick Saunders of the Denver Post reports.
Castro's demotion to Triple-A Albuquerque did not last long as after just one week, he's returning to Colorado's bullpen. He made three appearances for the Rockies' affiliate while on assignment and gave up a hit, walk, and one earned run over 2.2 innings. The 21-year-old will reassume a 3.75 ERA and 1.08 WHIP when he makes his return to the Rockies.