Hernandez (mouth) will begin a rehab assignment with High-A Jupiter on Friday, Joe Frisaro of MLB.com reports.
The Rule 5 pick started the season on the disabled list after having his wisdom teeth removed, though it seems like he's nearing a return to full action. Hernandez could join the Marlins' rotation upon his return, but he'll need to be offered back to the Astros if he's not kept on the 25-man roster all season.