Ross Barkley’s 96th minute equaliser at Stamford Bridge to make it 2-2 sparked incredible scenes in the dug-out between the two sets of backroom teams.
Footage showed Maurizio Sarri’s second assistant, Ianni, sprinting from the Chelsea bench and down the touch-line in celebration and gesturing towards Mourinho on his way past United’s staff.
And Ianni celebrated in the former Chelsea manager’s direction again on his way back to his seat, prompting an angry response from Mourinho who burst from his seat and had to be stopped by security and United colleagues from following Ianni down the tunnel.
The scuffle took several minutes to die down with players on the pitch breaking into arguments of their own as an entertaining Premier League contest turned ugly.
Speaking to Sky Sports cameras afterwards, Mourinho said: “I am not annoyed with anything. What happened was with Sarri’s assistant, and Sarri was the first one to come to me to say he would resolve the problem internally with me.
“After that his assistant come to me in Sarri’s office and apologised to me. I immediately said if you really feel that way, and you want to apologise, of course I accept apologies, and to forget it because I made lots of mistakes in my career.
“So I’m not going to kill you because of one. Forget it, it’s over, he apologised and it’s over.”
Sarri meanwhile declared his plans to deal with the situation “private” though former United defender Phil Neville told NBC Sports that the Italian should sack him.
And reacting to the melee on Match of the Day, pundit Shearer sympathises with Mourinho’s emotional reaction.
“Mourinho’s right there, that’s disrespectful,” reflected the legendary former striker.
“One to run past him in the first place and do what he did – Mourinho ignored that – but he did it again on the way back.
“I’m not surprised at all that Mourinho’s getting up and having a go at him.
“They’ve all apologised, Mourinho’s accepted the apology, I agree with him – move on and forget about it.
“But he’s got every right to have a go back there because you can’t do that.”
United were leading 2-1 before Barkley’s last-gasp equaliser having come from behind through an Anthony Martial brace.
The Frenchman’s second-half double was his first in two years for the Red Devils having been frustrated for game-time under Mourinho, consistently coming in and out of the team.
But Sky Sports pundit Graeme Souness thinks the 22-year-old still has what it takes to become one of the world’s best having failed to quite live up to his potential since his 2015 arrival from Monaco.
He said: “As a manager, you’re looking at players in training – he shows in matches as though he’s not that bothered. Every day in training is every match.
“You’ve got to keep impressing the manager, at 22 you’re looking to improve all the time, and it’d be a tragedy for that boy if he doesn’t achieve what God has given him, and he could reach the very top.”