Daily Mail claim Man United are only willing to allow a loan move for Pereira as Aitor Karanka is keen on acquiring his services for the season.
He also attracted plenty of interest last season, but Louis van Gaal blocked his proposed loan move and then failed to follow up on his promise of more game time on the senior side.
Mourinho wants Pereira to pick up more first-team experience away from Man United and a move to a Premier League side would drastically help with his development.
A move to Sunderland would do him good as he won’t be able to pick up many opportunities at Old Trafford this season under Mourinho and not wanting to let him go on a permanent deal is understandable as we all know how the Pogba situation played out.
Pereira may prefer to stay at United and continue his training at Carrington, but if he is given the opportunity to consistently play on Middlesbrough’s first-team in the Premier League he should grasp it with both hands.