Pellistri says he is enjoying his time in Spain, but he admits he would have liked to have had more time to acclimatise to life with United.
"I am very happy despite the rapid changes, faster than I imagined," the Uruguayan told ESPN.
"I was hoping to have a little more time in Manchester, but on the club's side they have organised what to do with each player.
"They thought that I would continue with the U23s but they thought it was time to make a move to the First Division."
Pellistri also opened up on what it's like training alongside his compatriot, Edinson Cavani, who has a wealth of experience plundering goals at the top level.
"It is something divine, to be every day talking about life with him," said Pellistri. "He helped me a lot at work, to kick, he taught me to use smaller studs because those were useful for him to avoid slipping because he had tried many.
"They are things that are helping you, they are forming you as a player and you make them your own."
He added: "It's like going to a top-level university. It teaches you everything you know and you absorb it and it fits."