The youngster was thrown into what had become a highly charged encounter following Marouane Fellaini‘s red card with just six minutes left.
He landed badly after leaping high to nod away a cross as Pep Guardiola’s men mounted one final onslaught on Man United’s goal in injury time.
And Mourinho, speaking after the game, confirmed fears that the 19-year-old had dislocated his shoulder.
“Fosu-Mensah was very injured in the last action – the last tackle,” he said. “He was on the floor and he is also an important player.”
Such a grievous, unavoidably long-term injury could not have come at a more inconvenient time for Mourinho. With Paul Pogba injured and Marouane Fellaini suspended for three games, the 54-year-old may have needed to call on the youngster for United’s clash with Swansea over the weekend. This could have been the perfect opportunity for Fosu-Mensah to mount a challenge on the Portuguese’s starting XI after spending this season on the periphery of proceedings.
But as things stand Mourinho only has two available central midfielders at his disposal – one of whom being a 35-year-old Michael Carrick, who will struggle to feature once again just three days after completing 90 minutes at the Ethiad – for Sunday’s game.