Now with Napoli, after a successful year with Inter Milan, Lukaku re-signed for Chelsea after initially being brought to England by the Blues.
But Lukaku never succeeded at Stamford Bridge before eventually finding his way back to Serie A.
Asked if he had another chance, would he take Lukaku back to Chelsea, Pastorello told AS: "In hindsight, probably not.
"But Romelu was included in the Ballon d'Or shortlist that year, something that had never happened before, and it was a record transfer from the Italian league.
"It was the right decision at the time. Then there are the human variables; no one could have predicted Lukaku's difficulties, perhaps not so much environmental ones, because he knew the club, but rather in his relationship with the coach.
"He came from an almost father-son relationship with (Antonio) Conte, and that difference in approach affected him in some way, along with the injury he suffered.
"If it hadn't been for that, the story would have been different."
Asked if Lukaku could've signed for Real Madrid, Pastorello added: "Real Madrid is the best club in the world, for several reasons. There was a small chance, but in the end, they were already focused on the big signing of Mbappé for the following year and didn't want to spend money on a loan."
He also said: "Lukaku has adapted well to Italy. When Antonio called him and asked him to join Napoli, he accepted immediately. It wasn't even discussed. It was the best time to work together again, and the results proved him right."