Santoni is a former Ajax video analyst and was at the club when De Ligt was coming through.
He said, "In Holland, you still see Barça as if it were Valhalla but Juventus is better for his development.
"In Barcelona, he would have had to defend the man again and he would not have improved. He would have done better for Barça but he would not have advanced.
"Now, he's learning another totally new way to defend and has become a total defender."
Santoni added: "We often forget that he is only 20 years old. He could not have been expected to be decisive when he first went there, but he has dominated everything in six months."