Rashford is set to undergo shoulder surgery to repair an injury that he has been carrying since the end of last year.
The forward is expected to be out for at least two months and is not expected to return to action before October.
Ole Gunnar Solskjaer will be without one of his most trusted attackers and it is likely to affect the prospect of James leaving Manchester United this summer.
It has been claimed that the Manchester United manager would be reluctant to further weaken his options out wide by letting the Welshman leave.
Amad Diallo is also expected to miss the start of the season as he will join pre-season later due to his involvement in the Olympics with the Ivory Coast.
Leeds head coach Marcelo Bielsa still has his eyes on James more than two years after losing out on signing him on a transfer deadline day.
Brighton are also interested but it seems the winger is likely to stay put at Manchester United for the moment.
