The two League leaders face each other in Turin on Saturday evening and Ferrara, who played for the duo, won’t pick one team over the other.
“I’ll be supporting both,” Ferrara, who had a brief spell in charge of the Old Lady too, told Tuttosport on Monday.
“I had some beautiful moments at both clubs and I can’t forget the past. I will, however, be watching the game as the Coach of Sampdoria…”
Juventus go into the game on an unbeaten League run which has now reached the 46-match mark.
“Sooner or later, all records come to an end,” the former Italian Under-21 boss added. “And Napoli can use this Sword of Damocles to stop Juventus.”
Despite both clubs clearly being Scudetto candidates this term, Ferrara doesn’t think the outcome of the game will decide anything.
“It won’t be a decisive encounter,” he continued. “We are only at the start of the season and there are other teams who could still enter the race.
“Juventus and Napoli certainly have a bit more than the rest, but they also have European games to deal with.”