There was never any doubting the magnitude of Sunday's Manchester derby but things took a turn for the worst in the tunnel, after the match.

Manchester City extended their lead atop the Premier League to a seemingly unassailable 11 points with a surprising, albeit thoroughly deserved, 2-1 win at Old Trafford.

Pep Guardiola's men turned their apparent Achilles' heel against their rivals with two goals from set pieces, virtue of David Silva and Nicolas Otamendi.

Marcus Rashford had found the net for the home side and Ederson was brilliantly called into action late on yet it was ultimately a blunt performance from United.

Such was the magnitude of the win, however, that not only are many fans handing City the title already but the players themselves were deemed to go overboard with their celebrations.

Jose Mourinho's post-match noise complaints and demands of respect soon turned into a tunnel brawl reminiscent of the infamous 'Pizza Gate' with milk and water thrown between players and staff.

Mikel Arteta reportedly left the stadium with a bleeding head and police officers had to be stationed outside of that dressing rooms. That's not mentioning Mourinho and Ederson's animated conflict, either.

The latest reports on the episode have revolved around Romelu Lukaku.

The Belgian endured a nightmarish performance in the derby with a solid attacking performance completely undermined by his culpability for both goals.

And, according to the Manchester Evening News, sources from Manchester City have noted that Lukaku completely lost his rag in the tunnel.

As the shoving match unfolded in a narrow corridor, Lukaku joined the 15 staff and players already scuffling.

The ex-Everton man did more than mimic the pushing, though, as he physically climbed upon Manchester United staff in an attempt to infiltrate the Manchester City dressing room.

Onlookers conceded that no punchers were thrown but that Lukaku's effort turned the incident into a 'rugby melee' with Mourinho at the heart of it.

You've got to admit, an apoplectic Lukaku trying to break into your dressing room is quite the concerning thought.

The incident avoided Michael Oliver's report with the match official not present yet an FA investigation will still be held over the skirmish.

Ultimately, though, no matter the response, City scored themselves a famous victory at Old Trafford and the title is now their's to lose.

Do you think Manchester City have wrapped up the title already? Have your say in the comments section below.