Having burst onto the scene in the second half of last season, the 19-year-old has struggled to establish himself in Mourinho’s plans during this campaign and is without a goal in 10 matches.
Former Celtic and Chelsea player Tony Cascarino feels the United manager is to blame for his “deterioration”.
“I don’t like the way he’s handled Marcus Rashford,” he told TalkSPORT.
“I just thought – start of the season, you bring Zlatan [Ibrahimovic] in, whatever you do get the kid in alongside him. Just give him a chance to show how good he can be.
“I’ve seen Rashford deteriorate quite a lot this year, and there is no other reason because he has been taken out of the firing line.
“Last year he was absolutely sensational at the end of the season for United and now I am looking at a young lad that has been given a new deal, but been taken out of the firing line, not playing much football now.
“He came on for a sub yesterday [for England against Spain], albeit not for a long time but he looked completely out of sorts.”