The Rays designated Herget for assignment Tuesday, Neil Solondz of the Rays Radio Network reports.
The move comes four days after the Rays selected Herget's contract, as they now need space for JT Chargois (oblique) to return from the injured list. Herget has a 2.45 ERA in 80.2 minor-league innings this season, so he could generate some interest on waivers.