Johnson was admitted to Boca Raton Regional Hospital on Thursday with an affliction that Kiffin described as “pretty scary.”
Kiffin did not know whether Johnson would be able to play again this season.
Prior to being admitted Johnson had been scheduled to travel with the Owls the following day to face Wisconsin.
Johnson, who was featured heavily in season two of Last Chance U while at East Mississippi CC last year, has been battling an arm issue that limited the strength on his passes as well as the accuracy.
Despite his struggles throwing the ball, Johnson proved in the season-opener against Navy that he was still a threat running it, rushing for 31 yards on four carries. He also completed two short passes for five yards, but his lone downfield attempt was underthrown and intercepted.
Kiffin had intended to use Johnson again at Wisconsin on Saturday, a game the Owls ultimately lost to the Badgers 31-14.
Daniel Parr drew his second consecutive start at quarterback in that game, completing 9-of-19 passes for 142 yards and a touchdown, and is expected to start on Saturday against Bethune-Cookman at Howard Schnellenberger Field.
“I would say that as of right now, yes,” Kiffin said.
FAU has yet to return from Wisconsin. Hurricane Irma closed South Florida airports, making such a return impossible. The earliest the Owls will get back to Boca Raton is Wednesday.