44-year-old Italian Mattiacci's motor racing experience is almost nil.
But even in that context, a team press conference in Barcelona last weekend was "bizarre", Speed Week correspondent Mathias Brunner reports.
He said Montezemolo made his "usual rallying calls", while Mattiacci sat beside him in complete silence.
"Apart from a brief message on the Ferrari website and a press conference in China, the former head of Ferrari North America has been silent," said Brunner.
In the Ferrari website message, the Maranello team said Mattiacci is "continuing with the task of analysing and evaluating the team and its working methods".
But Leo Turrini, an authoritative media source on Ferrari matters, pointed out that Mattiacci has now been in place at the head of the famous team for a month.
"During this time, he has almost never opened his mouth" publicly, he said on his Quotidiano blog.
"Now, we all agree that the Cavallino needs facts and not words, yet for decades, at least at the end of a grand prix, the boss has offered his version of events.
"Cesare Fiorio did it, Jean Todt, Stefano Domenicali. Mattiacci's silence is deafening," said Turrini.
Montezemolo, however, is backing Mattiacci to deliver eventually for beleaguered Ferrari.
"When he came, Todt was criticised a lot because he knew nothing about formula one, but then he managed to do a great job," he said.
"So it's like going back in time and I am sure that Mattiacci will do a good job."