The Dutchman blocked Pereira’s loan move last year and insisted he would play a role in the first-team, but did not feature for the rest of the campaign.
He has now joined Granada on a season-long loan after Mourinho informed the Brazilian he wouldn’t get an opportunity to play at Old Trafford.
Speaking about the former boss, Pereira claims he was disappointed not to get any minutes.
“Of course I was disappointed (last season). I wanted to play,” he said.
“Every player wants to play and I was disappointed I couldn’t play more minutes.
“I trusted the manager and it didn’t happen as I wanted it to but that’s life and I’ll learn from that as well.
“Now it’s different. I spoke with Mourinho and he was honest with me and that’s what I like.
“Maybe he (Van Gaal) was honest with me, but during the season a lot of things happened.
“I couldn’t say he’s a bad coach. I think he’s a very good coach, but unfortunately he couldn’t keep his word to me about that.
“I didn’t play but hopefully I can play now here (at Granada) and I can have a good season.”
He insists the atmosphere has changed at Old Trafford since the Dutchman’s exit.
“I think a lot of things changed and a lot of people changed,” he added. “People are more happy and more relaxed. It’s just a different atmosphere.
He featured for just two minutes between the closure of the January transfer window and the end of the season, Pereira would have undoubtedly been upset but Mourinho’s arrival at the club represents a new opportunity for him.
Hopes are he is able to impress the Portuguese boss while on loan with Granada so he can come back and slot into the United midfield.