Jose Mourinho returned to Stamford Bridge and was serenaded with 'You're not the Special One' for most of the afternoon as he witnessed his new side implode against the team he could not control last season.
Chelsea mauled United from start to finish and players like Chris Smalling, Daley Blind and Jesse Lingard will not relish the video reviews.
Gary Neville called some of United's efforts to repel Chelsea as 'absolute garbage defending' and that was being kind.
The travelling United support did their best to rally and back their team despite their woeful display on the pitch. In return, Conte was seen urging the Chelsea fans to match the away section in terms of passion and singing.
That, it seems, is what riled Mourinho and sparked the exchange of words at the final whistle.
There was much speculation about what Mourinho said to the Italian but Sky Italia believe they picked up these snatched words:
Don't do that at 4-0. 1-0 okay, but 4-0 is humiliation.
Mourinho was asked about the conversation on Sky Sports, after the game and initially attempted to brush off the question. Asked by Geoff Shreeves if he was happy with Conte's tub-thumping actions, Mourinho replied:
Of course not. That [chat] was between Antonio and myself.
This was a home-coming to forget but we don't suspect Mourinho will forget, or forgive, this one in a hurry.