The Pirates designated Hernandez for assignment Tuesday, Alex Stumpf of MLB.com reports.
A week after being optioned to Triple-A Indianapolis, Hernandez will now lose his spot on the 40-man roster in favor of Dennis Santana, who was claimed off waivers Tuesday. The 26-year-old southpaw owns a 4.82 ERA through 56 career MLB innings, but he has not been nearly as successful this season in the minors, posting a 7.04 ERA and 1.85 WHIP through 15.1 frames.