The Red Devils boss aired his disappointment after seeing a short-term deal pushed through, with the Portuguese suggesting that the 21-year-old should have been prepared to remain at Old Trafford and fight for his place - having signed a new contract with the club.
Mourinho did, however, add that United have the option to cut a season-long agreement short in January if they wish to do so.
Pereira is hoping that will not be the case, with the Brazil U23 international looking forward to gracing La Liga again – after spending time with Granada in 2016-17 – and proving that the comments made by his manager back in England were driven by frustration at seeing such talent removed from his ranks.
He told Marca: “It was difficult because they wanted me to stay in Manchester, but for me individually and for the options to play it was better to be here.”
Pereira added on Mourinho’s questioning of his decision: “It did not hurt, I talked to him before coming here.
“On the one hand I am happy because he likes me and I think he if thinks that I am not a good player he would not have wanted me to stay. So I think on the bright side.
“If I thought negatively it might hurt, but for me it is a good thing. I talked to him before coming here and I want to work hard stay all year. I am focused here.
“I want to be here and help the team all year, but I do not know what United wants in the future. I want to contribute the best and do the best all year at Valencia.”
Pereira made 37 appearances for Granada in all competitions last season and was handed his debut by Valencia in their recent 0-0 draw with Atletico Madrid.
He has made just 13 appearances for United to date, with all of those outings coming during Louis van Gaal’s time at the helm.