Blach cleared waivers and was outrighted to Triple-A Albuquerque on Tuesday.
The Rockies designated Blach for assignment Sunday.
Blach is scheduled to start Saturday's game against the Brewers in Milwaukee.
The Rockies selected Blach's contract from Triple-A Albuquerque ahead of his scheduled start Sunday against the Orioles.
The Rockies outrighted Blach to Triple-A Albuquerque on Friday after he cleared waivers.
Colorado designated Blach for assignment Saturday, Thomas Harding of MLB.com reports.
Blach is expected to start Tuesday against the Red Sox in place of the injured German Marquez (elbow), Patrick Lyons of JustBaseball.com reports.
Blach gave up one earned run on three hits and one walk while striking out a batter out of the bullpen in Tuesday's 4-3 loss to the Brewers.
Blach (3-4) picked up the win over the Pirates on Saturday, allowing two runs on seven hits and one walk while striking out five over 5.2 innings.
Blach (2-2) earned the win over the Guardians on Wednesday, allowing two runs on six hits and two walks over seven innings while striking out five.