Benfica sold Ederson to Manchester City earlier in the window and are said to be the most interested in completing a deal for Pereira.
However, Porto are also monitoring the situation after letting Iker Casillas leave the club in order to reduce their wage bill, with Sporting an option if they cash in on Rui Patricio this summer.
Pereira made a name for himself in the Liga NOS while on loan at Belenenses during the first half of the season and his case was helped after Mourinho called him the best Portuguese goalkeeper of the next generation.
Mourinho then gave him a run-out in an FA Cup game against Wigan, however, it won’t be enough if he is promised first-team football elsewhere with David De Gea and Sergio still in front of him at Old Trafford.
Should Real Madrid step up their interest in De Gea, we could see Pereira staying at United for longer as he looks to make an impact, but his current deal expires next summer and a decision needs to be made.