Hernandez was recalled from Triple-A Louisville on Wednesday.
Mere days after being sent back to the minors, Hernandez will return to bolster the Reds' bullpen once more. The 25-year-old has a high-octane arm and plenty of strikeouts to his name, although it is notable that he allowed a home run in each of his previous two appearances in the big leagues. He'll fill the roster spot of Devin Mesoraco (shoulder), who was placed on the disabled list.