The Rockies optioned Halvorsen to Triple-A Albuquerque on Wednesday.
Halvorsen has turned in a 3.31 ERA through 16.1 innings with the Rockies this season, but he'll end up as the odd man out of Colorado's bullpen following Jimmy Herget's (shoulder) return from the injured list. Based on the results Halvorsen has gotten in both the majors and at Triple-A (2.45 ERA in 14.2 IP), he's a safe bet to rejoin the Rockies at some point when the team needs a fresh arm.