Rafael has not been part of the United side since the third round of the FA Cup
The Mail says that manager Louis van Gaal is not impressed by the right-back, and doesn't like the 24-year-old's temperament or tendency to take risks in the game.
He has so far made nine appearances this season, his last in the 2-0 win over Yeovil Town in the FA Cup, and he has failed to hold down a place in the side - with Antonio Valencia recently preferred in the role, despite his position being more at home on the wing - and youngster Paddy McNair has also played in the role recently.
Rafael's contract has another season to run so it would represent the ideal time for Manchester United to cash in on him if they don't want to retain his services - or they will run the risk of letting him leave on a free the following summer, or talking to clubs from abroad in the January next season.
Given that the back line is probably one area of the field that United need to strengthen in the summer, it would be interesting to see if they go into the market looking for a right-back more in van Gaal's mould, or whether he will look to the youth system to see if he can find someone to mould into the type of player that he would like them to be - as he has done so often in the past at his other clubs.