Rashford and Martial were not happy with Mourinho's criticism of their form following the injury to Zlatan Ibrahimovic.
The Daily Mail says the pair's anger came at the end of last season.
However, Martial said this week he had benefited from Mourinho's tough love, while Rashford is a regular in his manager's team.
He explained: “He is hard with all of us and he is hard with me, there is no question. I know that it is for my benefit.
“I also know that he really likes me as a person so there is no issue about the discipline being for the wrong reasons."