Fellow BrazilianPereira, in an interview with Esporte Interativo, lifted the lid on Fred's work behind the scenes at United.
“In training and at the club, players know that the player is good," said Pereira.
"You notice when the guy arrives, who's the ace, who's the player who maybe can't take the level. Fred never had this problem with us. He's a very good player. Very good."
Pereira believes it's not unusual for a player to need a bedding-in period at a new club.
"So when he arrived and it wasn't working out, things are normal," added Pereira.
"In the first year he arrived he had to adapt to England, his family. These are normal things that maybe for fans who want to see this on the pitch, they don't understand.
"But with time now he relaxed, he's calm, the family is living well, he's training better every day. This year he was better at each game. And he's feeling good in the team, and now he can show his football.
"I already knew he was good, it was just for everyone outside to see the real Fred."