Star striker Zlatan Ibrahimovic and key defender Marcos Rojo were both forced off the Old Trafford pitch with knee injuries sustained during the Europa League quarter-final second leg win over Anderlecht.
Mourinho did not want to speculate as to the extent of the injuries but admitted that it did not look all that good for the crocked duo.
"I want to wait but my feeling is not good," he said.
"I don't think they are easy injuries but I prefer to wait until all the tests are done tomorrow.
"After tomorrow then I can speak what I feel because I am a manager, not a doctor."