Ruben Amorim's men pulled off a tremendous turnaround to condemn their bitter rivals to their eighth loss from 11 matches, as Bruno Fernandes and Amad Diallo cancelled out Josko Gvardiol's opener.
Man United sank their rivals despite losing the injury-riddled Mason Mount to another injury in the first half, forcing Amorim into an immediate tactical tweak as he brought Kobbie Mainoo into the fray.
Amorim is keeping his fingers crossed that Mount's problem is nothing severe, but the Red Devils boss may have been handed another concern ahead of the hectic run of festive fixtures.
According to journalist Steven Railston, Moroccan right-back Noussair Mazraoui limped out of the dressing room after Man United's triumph, but there is currently no indication how severe his problem is.
Mazraoui 'limps away' from Etihad after Man United victory
The former Bayern Munich man was lauded for a steadfast display against Jeremy Doku on the right-hand side, putting in six tackles and also winning both of his aerial duels in another praiseworthy performance.
Mazraoui has been heralded as one of the Red Devils' most consistent performers since joining over the summer, providing two assists in 24 appearances and making the first XI on 14 occasions in the Premier League.
The 27-year-old's versatility has also come in incredibly handy, as he has been deployed both as a right and left wing-back under Amorim, as well as occupying a position in their three-man central line at times.
As things stand, however, Mazraoui is seemingly a doubt for Thursday's EFL Cup quarter-final with Tottenham Hotspur at Old Trafford, which comes three days before Amorim's men host Bournemouth in the Premier League.
Man United's shock triumph over Man City did not improve their 13th-placed standing in the Premier League table, but they are just one point off the top half and within touching distance of the European places.
How could Man United replace Mazraoui for Spurs clash?
Mazraoui's adaptability and battling qualities have made him an indispensable asset to Man United in the current campaign, but Amorim is not short of alternative options in case the Moroccan is not passed fit for the imminent meeting with Spurs.
Mazraoui being selected on the right-hand side means that Diogo Dalot is often forced to occupy the left wing-back role, but the Portuguese could simply switch flanks on Thursday, thus opening the door for Tyrell Malacia to come back into the XI.
Alternatively, Amorim could move Diallo into a wing-back slot and promote a new face to the attacking line, most likely one of Joshua Zirkzee, Alejandro Garnacho or Marcus Rashford.
The latter two were surprisingly not in the squad for the Manchester derby, and Amorim was quizzed on whether Rashford and Garnacho will be back for Thursday's EFL Cup quarter-final.
As things stand, Luke Shaw will be Man United's only definite absentee for the Spurs game as he manages a calf injury, while Jonny Evans missed Sunday's win due to his knock and will need a once-over.
Written by
Ben Knapton