F Erik ten Hag was watching in Amsterdam he must have been wondering if this was indeed the same Manchester United team.

Why does this always happen?

14Manchester United made a positive start to life after Erik ten HagCredit: Reuters14The Red Devils scored four goals in a chaotic first halfCredit: Getty14Ruud van Nistelrooy took interim charge as talks continue with Ruben AmorimCredit: Getty14Casemiro whipped a sensational opener into the top corner

14Casemiro impressed with two goals for Van Nistelrooy’s men14Bruno Fernandes thrived in the win over Leicester

The old boss goes, his assistant takes over and the team transforms overnight.

It makes you wonder what Ruud van Nistelrooy was doing on the training ground in the first place.

Much of this victory that put the Red Devils into the quarter-finals of the Carabao Cup was down to the strength of the opposition.

Leicester City fielded a team with nine changes and was similar in strength to that which drew 0-0 with Walsall in the last round before winning on penalties.

United by contrast were strong, Van Nistelrooy wasn’t going to pass this chance up to be a winner from the Old Trafford dug out.

Mind you to be fair to him whoever pulls on a Man Utd shirt nowadays nothing can be guaranteed.

So credit Van Nistelrooy for getting a tune out of this lot just two days after Ten Hag was dismissed.

The regular boos heard here became cheers and smiles replaced frowns and shaking heads.14Alejandro Garnacho tucked home Man Utd’s second of the eveningCredit: Rex14Bilal El Khannouss pulled one back for LeicesterCredit: Getty14Fernandes’ deflected free-kick made it 3-1 moments laterCredit: Reuters14Casemiro netted his second of the night and Man Utd’s fourthCredit: Getty

It was reminiscent of.. well when they played Barnsley in the last round and won 7-0 but not much else in recent memory.

Even Casemiro shone brightly.

With two goals and an assist he had the home crowd buzzing at the break even if familiar failings at the other end kept Leicester just about in it at 4-2.

It is fair to say the Brazilian has not pulled up any trees since coming here but with his first strike he nearly uprooted the goal.

Of the 150 goals Van Nistelrooy scored in 219 games for this club only one of them came from outside the box.

So he was open mouthed in disbelief when he saw what Casemiro did in the 15th minute as he received a ball from Alejandro Garnacho and then from 30 yards hammered a shot into the top right hand corner in off the underside of the bar.

The former Real Madrid star ran to the corner flag and tapped the United club emblem with his hand.

Why he had gloves on his hands was another matter.

The home side’s second followed in the 28th minute as this time Casemiro set the move which led to it going with a chipped a ball down the right wing.

Diogo Dalot fired it to the far post and Garnacho slammed it into the roof of the net.

Back came Leicester in the 33rd minute as stand in goalkeeper Altay Nayinidr’s weak punch was fired back past him by El Khannouss.

The goals were flying in and just three minutes later Bruno Fernandes free kick was deflected in off James Justin’s head.

Onto the 39th minute and Casemiro on target again as this time he followed up his own header which hit both posts to net the rebound.

What was going on here, this isn’t normal United, dominating a game.

Ah wait, in first half injury time a ball into the box skimmed off Casemiro’s header bounced off Dalot and was turned in by Conor Coady.

14Conor Coady pulled another one back for Leicester before half-timeCredit: Getty14Fernandes bagged his second of the eveningCredit: Reuters

Game still on, given this was United.

Back came the teams for the second half and the roar of ‘Ruuuuuuud’ went out around the ground as the interim boss reappeared.

Leicester had been given a lift with that goal and rallied from the restart.

Any brief hope they had of a fight back was then extinguished with Caleb Okoli’s sloppy back pass just short of the hour.

Captain Fernandes was on to it, rounded the keeper and fired it home from close range.

He reacted with a defiant punch of the air.

Even he, with his stats, has not escaped criticism but have no doubt about how much he genuinely cares about the club.

Van Nistelrooy will be in charge again for Sunday’s visit of Chelsea which had looked daunting.

They will go into it, however, with some confidence restored.

Incoming boss Ruben Amorim will watch this in Lisbon and know that at least he has something to work with.

On the night before Halloween, the ‘Theatre of Screams’ headlines were not needed.

14Ruben Amorim is expected to be appointed the next permanent Man Utd managerCredit: Getty