Despite netting 55 times in 105 appearances for the Bianconeri, a proven frontman was deemed surplus to requirements in Turin over the summer.
A €100 million (£88m/$115m) deal for Ronaldo saw him nudged down the pecking order and eventually out of the door to San Siro.
Higuain has responded positively in new surroundings, netting six times in seven appearances for Milan.
Juve icon Del Piero feels the 30-year-old frontman has the look of a player trying to prove a point, telling Sky Sport Italia: “AC Milan need him so badly, both for his goals and for his leadership.
“Everybody runs to hug him whenever he scores, this proves how happy he is in Milan and proves he’s settled in well.
“Before his move to Juventus, he used to complain much more, at Juve he has improved and he has learned to play for the team as well.
“However, I think he is angry with Juventus. He wanted to take his revenge after being kicked out of Juve.
“He had positive seasons at Juve but he was sold, I think that’s the reason for Higuain’s anger.
“Did you notice his celebrations? He opens his arms like he wants to be hugged. He is at AC Milan to solve their problems, he knows that and he loves it. He feels great in the group.”
The deal which took Higuain to Milan is an initial loan agreement.
The Rossoneri do, however, have the option to turn that move into a €36m (£32m/$41m) permanent deal at the end of the season.