It's fair to say there is little love lost between the Manchester clubs following a brawl in the Old Trafford tunnel on Sunday.
City were celebrating a pivotal 2-1 victory in their inexorable march towards the title.
Jose Mourinho, on the other hand, couldn't help but feel a little annoyed by the manner in which United's rivals were revelling in the result.
According to the Mirror, the Red Devils have laid the blame for the fracas firmly at the feet of the City squad, amid claims they were blasting loud music from the dressing room.
Only the players and staff themselves truly know what went on and it's a pity there is no CCTV covering that corner of the Theatre of Dreams.
One theory which had been doing the rounds was that it was all instigated by a comment made towards Zlatan Ibrahimovic.
It was claimed, via Spanish publication Marca, that the Swedish striker had been right at the heart of the brawl - not so much because of anything he did, but because City players allegedly shouted at him:
"Ibra, you talk a lot but you move a little."
What Zlatan was really doing
If that was indeed the case then surely Ibra, master of one-liners, in recent months attracting more interest as a comic entertainer than as a footballer, would have taken it in good jest.
The reality, at least according to the Manchester Evening News, is that he was actually in the medical room, receiving treatment for his knee.
While it was all kicking off, the former PSG, Barcelona, and Inter Milan star was spending the time with club doctors.
The 36-year-old has been playing a bit-part role and is yet to find the back of the net since making a surprise return to action last month, considerably ahead of schedule given the severity of the knee ligament damage he sustained in April.
The Sun claim that there are growing concerns among United officials that he'll never rediscover the form which saw him top score for the club last season with 17 league goals.
That's to be expected, but the fact he was focused on his recovery while all around him his team-mates were losing their heads, is yet another promising sign of his belief that the old Zlatan will be making a comeback soon.
Did City disrespect United with their celebrations? Have your say in the comments.