Four productive years in Serie A saw Pogba establish himself as a global superstar, with United investing £89 million ($117m) to bring him back onto their books in the summer of 2016.
The 25-year-old is now a World Cup winner, but he has found the going tough at times in the Premier League as his form and attitude continue to be called into question.
A return to Juve has also been mentioned, with Pirlo telling Tuttosport of those rumours: “It would not surprise me because Juventus is looking for the best and if one player goes away it is not said that they cannot return.”
Juventus have refused to be drawn on links to Pogba, but displayed their ambition once again during the last transfer window as they completed a €100m (£89m/$117m) deal for five-time Ballon d’Or winner Cristiano Ronaldo.
The Portuguese has helped to raise expectations and the collective quality at the Allianz Stadium, despite being yet to open his goal account.
He is expected to be a positive influence on those around him, with Pirlo calling on Paulo Dybala to model himself on the former Real Madrid star and force his way back into the fold after another spell on the bench.
The legendary playmaker said of the Argentine forward: “Accepting not starting from the beginning is not easy for anyone. Paulo must do everything to play as much as possible.
“If he starts training with the desire of Ronaldo then it will be difficult to leave him out.
“When you do not play, it means that you have to do something more.
“The qualities of Dybala are not in question. To become a fundamental player for Juventus he must find something inside him, he must do it first of all for himself.”
Juve are set to return to action after the international break on Sunday with a home date against Sassuolo.