Manchester United played out a 1-1 draw with Anderlecht in the first leg of their Europa League last-eight clash in Belgium last week.
And Henrikh Mkhitaryan broke the deadlock in the first half to give Manchester United a 2-1 aggregate lead in the second leg at Old Trafford.
However, Anderlecht midfielder Sofiane Hanni equalised before half-time for the visitors to leave the quarter-final tie all square.
Rojo suffered an injury in the 23rd minute as Manchester United’s defensive crisis worsened with Phil Jones and Chris Smalling out injured.
And Ibrahimovic appeared to pick up a knee problem after Manchester United’s leading goal-scorer fell awkwardly at the end of normal time at Old Trafford.
Speaking to BT Sport about Ibrahimovic and Rojo suffered injury setbacks, Manchester United boss Mourinho said:
“I don’t think they are easy injuries. I prefer to wait until all the tests are done and then speak what I feel. I can’t do that I am just a manager and not a doctor.”
Pressed to give a more thorough update on the Manchester United duo, Mourinho added: “It is fairly negative.”