United were ruthless after Saints went down to 10 men when Alexandre Jankewitz was sent off inside two minutes, going 4-0 up before half-time and then adding three more after Jan Bednarek saw red towards the end.
It equalled the biggest ever Premier League win set by United’s victory over Ipswich in 1995 and Southampton’s defeat by Leicester last season.
Manchester United boss Ole Gunnar Solskjaer says they have remained level-headed this week
United thumped Southampton 9-0 on Tuesday – in a Premier League record-equalling victory
However, Solskjaer believes the circumstances behind the thumping win mean that his players won’t be over-confident against Everton on Saturday.
‘We’ve not mentioned the game at all really, all the focus has been on Everton,’ said the United boss.
‘You’ve got to take the good with good and bad with bad sometimes. What the boys took from that one is we did the right things and kept good habits.
‘I don’t think anyone will get carried away with the scoreline because we played against 10 men for nearly the full game and it’s demoralising when they lose the players like they did.
‘When we got to 2-0 the game was more or less over. It was just about doing the right things.’
Everton are eight points behind United but have two games in hand, and Solskjaer will be keen to increase the gap between the two clubs.
He praised the job Carlo Ancelotti has done in his first full season at Goodison Park, saying: ‘He’s a manager that you really look up to and respect.
‘He’s a winner everywhere he’s been. He influenced PSG, what he started there, what he’s done at AC Milan, Chelsea, Real Madrid, you can see that at Everton as well.
‘They have started the season fantastically and won the last four away games. It’s a team you know you’re in for a battle when you play against them.’
Solskjaer is hopeful Edinson Cavani will be fit after coming off at half-time against Southampton with an ankle knock, but Eric Bailly is doubtful.