The Argentine, who played for PSG between 2011 and 2018, was in Paris this week for a Champions League sponsor event and spoke glowingly about the player who arrived from Barcelona in January for around €8 million.
Dro has made seven appearances for PSG so far, scoring once, as he gradually finds his feet in Ligue 1 after coming through La Masia.
Pastore, now working as a player agent, was effusive.
"He has class. I really enjoy watching this kid play. He is still very young. His moment will come at Paris, I am sure of it."
He explained why Fernández fits the current PSG project.
"He has the profile to play for this PSG. He has already played and shown many positive things."
The number 27 carries a particular weight in Paris, associated above all with Pastore's seven years at the club. Fernández wore the same number at Barcelona, which made the choice natural — and meaningful to his predecessor.
"I am very happy that it is a player like him who has inherited the number 27, which was mine and which people associate with beautiful football and talent."
He left no doubt about his confidence in the teenager.
"I believe Dro has talent to spare. I am very happy that he wears my number and I am sure he will have a great deal of success for many years here in Paris."
Dro signed for PSG on a contract until 2030. At 18, he is still developing, but Pastore's blessing — from the man who first made that shirt number mean something at the club — carries weight.