Erik ten Hag was plunged into his worst nightmare as Man Utd's problems were exposed at Man City

Just when Manchester United thought it was safe to feel positive again, just when we thought there would be a Manchester derby worthy of the name, this was an annihilation so brutal, so one-sided, that Erik ten Hag was plunged back into his worst nightmare.

If the United manager thought that being 4-0 down before-half-time at Brentford in August was an horrific aberration, never to be repeated, here he was just seven weeks later in the same deep, dark hole.

Only this time Manchester City threatened to make it even worse for the Dutchman. The fact the eventual damage was only 6-3 was largely down to Pep Guardiola’s exhilarating side taking their foot off the gas in the second half and conceding three goals that distorted the scoreline.

When City hit United for six at Old Trafford in October 2011, Sir Alex Ferguson’s team were punished for chasing the game with 10 men. They were never in this one.

Four straight wins since the Brentford debacle had raised hopes that United were moving in the right direction under Ten Hag. Let’s not forget, the Dutchman arrived here as the Premier League manager of the month.

But the green shoots of recovery were trampled into the Etihad turf so mercilessly that you had to question just how much progress has really been made.

United’s fragile confidence crumbled in the face of an irresistible City team performance and the individual brilliance of Erling Haaland, Phil Foden and Kevin De Bruyne.

Ten Hag made a bold team selection, picking only one defensive midfielder in Scott McTominay, perhaps hoping it would send out a message to his players, but the decision backfired as United were overrun.

It took him an hour to end McTominay’s misery by replacing him with Casemiro, and 70 minutes to double up on holding midfielders by sending on Fred. By then, United were 5-1 down and there were more empty blue seats than United fans in the away section.

The team selection allowed Christian Eriksen to start but the Dane must also have suffered flashbacks to Brentford.

Inexplicably, he was left marking Haaland when City’s prolific Norwegian headed the second goal.

Much was said in the build-up about Lisandro Martinez’s lack of height against Haaland, but surely the plan wasn’t for Eriksen to pick him up at a corner?

‘Of course not,’ snorted Ten Hag indignantly, pointing to the fact that Raphael Varane had been hurt seconds earlier.

Varane limped off before half-time, having lost Foden for the first goal and Haaland for the third.

Eriksen and Varane have been key figures in United’s revival. So have Martinez and Tyrell Malacia, but they were beaten to the punch for the fourth and fifth goals.

Malacia was hooked at half-time having been booked. Diogo Dalot was shown a yellow card by referee Michael Oliver after 90 seconds, meaning both United full-backs were compromised in their efforts to stem the flow of City attacks down either flank.

None of Ten Hag’s players emerged from this with any credit, except perhaps substitute Anthony Martial who led a meaningless late fightback.

It took Bruno Fernandes 39 minutes to fire their first shot in anger from 30 yards, and they never seriously tested City’s unfamiliar defensive partnership of Nathan Ake and Manuel Akanji.

A revitalised Marcus Rashford didn’t lay a glove on them. Former City man Jadon Sancho was utterly anonymous, and left the field to howls of derision when Ten Hag made his fifth and final substitution.

That left Cristiano Ronaldo stewing on the bench. ‘I wouldn’t bring him in out of respect for Cristiano and his big career,’ said Ten Hag, clearly feeling that he has done Ronaldo a favour.

Every United manager since Ferguson in 1987 has lost his first league derby against City, so Ten Hag is not alone in that respect. But the manner of this humiliation is a huge backwards step he could not have expected.