The former Rangers captain says the fee paid by Juve for the Brazilian was crazy.
Amoruso said: "This is something I also said. They did not need him.
"Melo is a good player but not worth 25 million euros, partly because they spent the same amount to bring to Turin Diego, who is someone that will change the game and makes you win.
"Juve also has two other similar players: Christian Poulsen and Momo Sissoko. I complimented (Fiorentina sports director) Pantaleo Corvino who made an amazing profit."