The France international was taken off in the closing stages of United’s 2-0 win over Burnley on Sunday, with Mourinho admitting he was unsure if the problem was simply muscle fatigue or a more serious concern.
Although he would not specify the nature of the injury, Mourinho has now said that Paul Pogba will be unavailable for the trip to the Etihad Stadium this week.
Asked if Paul Pogba or Ander Herrera would be fit, he told a news conference: “Paul, no. Herrera, yes.”
He added that Antonio Valencia will return after having been rested for the win at Burnley, but centre-backs Chris Smalling and Phil Jones are still out.
“We go with what we have, we fight with what we have. I trust the boys. We are fighters and we go,” he said.
United are already without Zlatan Ibrahimovic and Marcos Rojo, who have knee ligament injuries, while Juan Mata is yet to recover from groin surgery.