Juventus beat Parma 3-0 in the league on Sunday.
The Parma boss had his first defeat of the season.
His team were beaten by a side that won their previous game by a combined total of 11 goals.
Parma had to settle for a 1-1 draw, thanks to two goals from Paulo Gazzaniga and one from Lorenzo Bonazzi.
Juventus lost their second game of the Serie A season, against Udinese, 4-0.
It is the first time in the Serie B era that Juventus have been beaten 3-1 by the Italians.
Their second game is against Bologna on Wednesday.
Piacenza reached the final of the Parma Superleague, the top tier of Italian football.
The team were relegated to Serie B in 2012 after four years in the top flight.
Piacentini will be replaced by Antonio Conte, who has not lost since taking over at Juventus from Francesco Totti.