Dorgu scored a stunning goal to give his side the lead in North London but was forced off in the 81st minute after he picked up the injury. Mikel Merino then looked to have rescued a point for the home team before substitute Matheus Cunha scored a sensational winner for his side.
United have not placed a specific timeframe on Dorgu's return to action, though early indications are that he could miss the next eight matches. It means Michael Carrick might be without the rejuvenated star until April and will have to make a change to his starting line up.
Here is how we think United could look without him.
Lammens has been the unsung hero for United this season and is crucial in goal.
1. GK - Senne Lammens
Lammens has been the unsung hero for United this season and is crucial in goal. | Getty Images
Maguire has been excellent across consecutive matches and will take some shifting in defence.
2. CB - Harry Maguire
Maguire has been excellent across consecutive matches and will take some shifting in defence. | Getty Images
Martinez is the best left centre-back at the club and has to start when he is fit.
3. CB - Lisandro Martinez
Martinez is the best left centre-back at the club and has to start when he is fit. | Getty Images
Dalot was good against Arsenal and is still the best right-back for the current system.
4. RB - Diogo Dalot
Dalot was good against Arsenal and is still the best right-back for the current system. | Getty Images