Rusin will take the spot of righty reliever Jason Motte, who was put on the 15-day DL with a right rotator cuff strain. Rusin was 2-4 with a 4.12 ERA in 12 games before being sidelined by a strained left shoulder.
Rusin made three rehab appearances for Triple-A Albuquerque, going 0-1 with a 5.79 ERA. Rockies manager Walt Weiss said he will be used out of the bullpen for now.
"Initially, we look at him as a guy who can give us length if we have to go to the bullpen early," Weiss said. "But I don't rule out using him as late as the fifth or sixth inning right now."
Motte, 34, is 0-1 with a 5.66 ERA in 26 appearances this season. He began the regular season on the disabled list with a right shoulder strain before being reinstated May 25. The latest injury is not related to the earlier setback, Weiss said.