Last week, Fox announced that in midseason American Idol will air on Wednesday and Thursday evenings.
The move means that Fringe, which currently airs on Thursdays, will be pushed back to Friday nights.
Although programmes airing on a Friday tend to struggle in the ratings, Reilly told Deadline that he does not expect Fringe to suffer.
"Fringe has a very particular, loyal audience," he said. "If [Fringe] could stay near the current levels, we'll get a big trade-up on Friday and solve our problem there."
Fringe continues on December 2 at 9/8c on Fox.