The Englishman was replaced with captain Wayne Rooney after 77 minutes and Mourinho claims it was only then that he settled for a draw.
The Portuguese boss has explained how it forced him to change his game plan against Jurgen Klopp’s side at Anfield.
“I think we missed a little bit of sharpness through the middle,” he said.
“I was expecting more penetration and I was thinking about playing Rashford in the position behind Zlatan but he had cramp and I made a change. At that moment I thought it would be difficult to win now, so let’s not lose it.”
Rashford has quickly worked his way into an indispensable member in the squad once again after many believed he’d be left out due to Zlatan Ibrahimovic‘s arrival at Old Trafford.
He has knocked down all expectations of himself since his debut in February and hopes are his injury is nothing serious as Man United head into a busy schedule of fixtures.
Mourinho’s side face Fenerbache, Chelsea, Man City, Burnley and Swansea all with three day intervals and Rashford will be a key member for the squad.