Bubic (elbow/shoulder) suffered a setback after beginning his rehab assignment Tuesday with Triple-A Omaha, MLB.com reports.
In his first rehab start while recovering from left elbow soreness, Bubic was knocked around for five earned runs across 1.1 innings Tuesday and apparently emerged from the outing with a shoulder issue. The southpaw is scheduled to see a doctor over the weekend to determine the next steps. Prior to landing on the injured list in mid-May, Bubic posted a 3-2 record with a 4.11 ERA, 1.23 WHIP and 51:26 K:BB across 50.1 innings (nine starts).