It came at Old Trafford against United's greatest rival in the season when the Red Devils should be challenging for the title after so much more spending.

"This is the worst feeling," Solskjaer said.

"You feel rock bottom."

Maybe all that is keeping Solskjaer in the job is the lack of chants aimed at him by United's fans.

There were enough of those being directed his way by the visiting Liverpool fans, gloating as the goals flowed from the fifth minute in the 202nd meeting of two of English football's biggest rivals.

The Reds' biggest ever victory away to Manchester United was begun by Naby Keita and the porous United defence allowed Diogo Jota to score in the 13th minute.

Mohamed Salah picked up the scoring to net for a 10th consecutive game for Liverpool, with two before the break.

It meant United went to halftime four goals behind in a Premier League match for the first time.

The scale of Liverpool's success at United is highlighted by Salah, early in the second half, becoming the first opposition player to score a Premier League hat-trick at Old Trafford.

"As long as the team keep winning, I'm more than happy," Egypt forward Salah - who has now surpassed Didier Drogba as the Premier League's top-scoring African player - said.

Nine games into the league season, the record 20-time English champions are already seven points behind second-placed Liverpool - with leaders Chelsea a further point away.

"We have conceded too many goals, too many easy goals and that's a concern," Solskjaer said.

"I am still thinking about tomorrow's work, I can't say now I have felt any worse than this."

United look no closer to winning a first Premier League title since 2013 - with Solskjaer under contract through to 2024.

"It's not easy to say something apart from it's the darkest day I've had leading these players and we weren't good enough, individually and as a team," Solskjaer said.

His sentiments were echoed by Cristiano Ronaldo on social media.

"Sometimes the result is not the one we fight for. Sometimes the score is not the one we want. And this is on us, only on us, because there's no one else to blame," United star Ronaldo posted on Instagram.

"Our fans were, once again, amazing in their constant support. They deserve better than this, much better, and it's up to us to deliver. The time is now!"

Liverpool's victory margin is United's joint-biggest home loss in Premier League history - after Manchester City in October 2011 and Tottenham in October 2020 recorded 6-1 thrashings.

Next up for United is a trip to Tottenham on Saturday, with Nuno Espirito Santo's side also coming off a loss.

Spurs went down 1-0 to West Ham with Michail Antonio getting ahead of marker Harry Kane to score from a corner in the 72nd minute.

In Sunday's other game, Youri Tielemans and James Maddison scored to give Leicester a 2-1 victory at Brentford.

Australian Associated Press