Manchester United manager Ole Gunnar Solskjaer confessed the 6-1 home defeat to Tottenham was his worst day in football.
Ten-man United sunk to their joint heaviest Premier League defeat ever as Jose Mourinho's men ran riot at Old Trafford to darken the club's already bleak mood significantly.
Solskjaer, whose position will surely now come under threat after this embarrassing loss, saw his side capitulate after going in front inside two minutes through Bruno Fernandes' penalty.
Son Heung-min and Harry Kane scored two each, with Tanguy Ndombele and Serge Aurier also getting on the scoresheet as Mourinho's men made an impressive statement.
The inquests have already begun, with former Red Devils full-back Patrice Evra describing them as a shambles and club great Gary Neville said their performance was "an absolute shambles" as United matched the 6-1 loss to Manchester City in 2011.
The Norwegian, whose club are reportedly closing in on a deal to sign Alex Telles from Porto and free agent Edinson Cavani, said he shoulders the blame.
"It's very embarrassing, it hurt all the players," said Solskjaer. "It hurts me as the manager. It's my worst day ever.
"I'll hold my hands up, I'm responsible for this. I've lost 5-0 with United and we've lost 6-1. We've lost big results before and always bounced back.
"I promise we'll do everything we can to turn this around.
"We know how good they can be but today all our mistakes came almost like Christmas everything at once and if you make too many mistakes against a good team and you'll be punished."
Martial saw red just before the half-hour after he slapped Erik Lamela in the face when the Argentinian appeared to put his arm in the Frenchman's neck.
Lamela delayed his reaction, which left Solskjaer fuming.
"For me of course there are two emotions," he added. "Well done Anthony for not going down and not trying to con the ref to send Lamela off. He puts his arm on Anthony's throat.
"But Anthony knows he can't react like this. But then come on, you can't go down like that, it's absolute joke for me. A lad can't react like that and wait for two seconds before he goes down.
"If that was my son he would live on water and bread for two weeks, that's not how I want my players to react."
Victory will be sweet for Spurs, who have scored 11 goals in their last two away games and still have Gareth Bale to come into their side after the international break.
This win comes on the back of four games in eight days, but they showed that under Mourinho this season they could challenge at the top end of the league.
It started badly for them as Fernandes scored a penalty that was awarded after just 31 seconds but things soon perked up as Tanguy Ndombele's leveller, Son's brace and a Kane effort saw Spurs become the first team in the Premier League era to score four first-half goals against United.
Serge Aurier and Kane's penalty made it a memorable afternoon after the break to leave Mourinho, on his second visit back to Old Trafford honoured.
— Tottenham Hotspur (@SpursOfficial) October 4, 2020
"To win 6-1 against Manchester United at Old Trafford is an honour for all of us, considering the dimension of Manchester United and Old Trafford," he said.
"The pleasure is not the 6-1, the pleasure is the performance and three points which we really need after losing points at home against Newcastle.
"The target, objective is every match we go to win. I told the players in the last couple of days 1000 times a good result at Old Trafford is to win.
"Of course if you draw it's not a bad result but that's the kind of mentality we must get. It was a great performance, a great result. We have seven points, so our position in the table is so-so."
Mourinho was sacked at Old Trafford in December 2018 and admits he has sympathy for the man who replaced him.
"I have sympathy for Ole because of the result," Mourinho said. "I don't remember that I lost by six but I lost by five, I lost by four. I know how we hurt.
"I know it's very very important that the winning manager behaves in a way where he shows sympathy. Of course I want to win, and of course I want to win by seven, not by six. Don't get me wrong.
"But it's sympathy in our behaviour. Today was him, tomorrow is me. Of course I feel sympathy for him. I can imagine that tonight he's not going to sleep very very well. But this is the hard life of us."