Sarri, who took over at the Italian champions after leaving Chelsea in the summer, has failed to stamp his authority in Turin and has come under increasing pressure after Juve slipped off top spot in the Serie A table following Saturday's shock defeat to Verona.
The 61-year-old insisted he was not fazed by the scrutiny at his press conference ahead of Thursday's Coppa Italia clash with Milan by saying: "If I'd wanted to avoid pressure and facing tough tests, I'd have applied to work for the Post Office."
The Italian Post Office did not take kindly to the words of the 61-year-old, and responded with a statement on Twitter.
"Contrary to what Mr. Sarri claims, pressure does exist at the Post Office," it read.
"It is responsible to citizens, businesses and public administrations. Poste Italiane invites Mr. Sarri to spend a few minutes of his precious time discovering that the Poste is the largest company in the country, and ranks third, worldwide, among Italian companies in terms of image and reputation. We are waiting for him in one of our 15,000 centres so that he can see our daily work in person.”
Juventus will face Milan in the first leg of their Coppa Italia semi-final, with two Serie A games to come before they return to Champions League action in the last 16 against Lyon at the end of the month.
It is an important time for the club who will be expected to fight on all three fronts, and after eight Serie A titles on the bounce, surrendering their Scudetto is unthinkable and unacceptable.