Rusin (oblique) completed a bullpen session Monday, Patrick Saunders of The Denver Post reports.
It was Rusin's first mound work since he first suffered a right oblique strain during a March 3 Cactus League appearance, and though he appears to be progressing, he's likely missed too much time this spring to seriously contend for the open spot in the Rockies rotation. That role is expected to fall to German Marquez, which likely puts Rusin on tap for a long-relief role to begin the season.