Pereira made the move on Spain's transfer deadline day, with Manchester United confirming he would spend the season with Marcelino's side.
United manager Jose Mourinho said he did not agree with the decision and that Pereira should be "fighting to be a Manchester United player," per Ian Whittell at the Daily Telegraph.
Per Las Provincias (h/t Samuel Luckhurst at the Manchester Evening News), Valencia chief executive Mateu Alemani recently said the Red Devils can recall Pereira should they wish: "Of course Manchester United have an option to get the player back. They can sign the player on one condition, but I am not going to say what kind of condition this is. It's confidential, and it's something that I am not going to reveal."
Manchester United have injury problems in midfield, and Mourinho said on Friday that Paul Pogba's hamstring problem is a "long-term injury," per BBC Sport.
Luckhurst said that United's injury situation is a missed opportunity for Pereira:
If United were to recall Pereira, Valencia would be due compensation, per Spanish football journalist David Cartlidge:
Pereira has made four appearances in La Liga for Valencia this season, providing one assist, per WhoScored.com.
Despite United's injury problems, it seems as though he has more chance of regular minutes at the Mestalla than at Old Trafford this season, although his decision to leave has clearly unimpressed Mourinho.
Elsewhere, Manchester United may have to "spend big" if they are to land Antonucci, who recently signed a new deal with Roma that runs until 2022, per Transfermarketweb (h/t Joe Short in the Daily Express).
The Red Devils were one of several clubs said to be monitoring the 18-year-old, who is highly rated but yet to start for Roma's first team.
The striker has clearly impressed football writer Liam Canning:
Marcus Rashford has also started the season strongly, with five goals and an assist, per WhoScored.com.
So too has Anthony Martial, forming a prolific attack alongside Lukaku and Rashford, as sports journalist Adam Joseph noted:
Mourinho has a host of youthful attacking options in his squad, and there looks to be little need to strengthen the forward line, particularly with a teenager who has yet to make his first-team debut.