Ruud van Nistelrooy enjoyed a winning start as Manchester United’s interim manager as his side thrashed Leicester to reach the Carabao Cup quarter-finals.

Two days after Van Nistelrooy was appointed as stand-in following the dismissal of Erik ten Hag, his pre-match demand for entertainment was met in full.

Casemiro started the fun with a sensational long-range strike and by half-time the Brazilian had another as he followed up an initial header that bounced off both posts by driving home from eight yards.

In between those efforts, Alejandro Garnacho fired home his fifth goal of the season and skipper Bruno Fernandes’ free-kick deflected in off Leicester full-back James Justin.

It wasn’t perfect from the hosts as old defensive frailties returned to allow Bilal El Khannouss and Conor Coady to score before half-time. The latter effort came after the ball had struck Diogo Dalot and bounced invitingly for the former England man to apply the first-time finish.

But in front of Sir Alex Ferguson, back at Old Trafford for the first time since being told he was being stripped of his paid ambassadorial role, and United’s powerbrokers who are aiming to replace Ten Hag with Sporting boss Ruben Amorim, the hosts always had an element of control.

Fernandes added a fifth on 59 minutes when he took maximum advantage of Caleb Okoli’s under-hit back.

United will travel to face Tottenham in the quarter-finals, with that tie lined up for the week commencing 16 December.

Van Nistelrooy’s popularity in these parts comes from his status as United’s ninth highest all-time scorer.

Remarkably, his 150-goal haul included just one scored from outside the penalty area. It partly explained his joy at seeing Casemiro’s opener fly into the top corner from almost 30 yards.

The Brazilian was helped by Leicester’s complete failure to press the ball from Garnacho’s inside . But the former Real Madrid man had time to take a touch to set himself and then strike his shot with accuracy and venom, giving Danny Ward no chance of keeping it out.

Van Nistelrooy’s elation was plain to see as he raised both fists and turned to the crowd, who had applauded him onto the pitch before the start of the game.

Casemiro, 32, has been used as an example of the profligacy in United’s transfer spending during Ten Hag’s time at the club. There is still over 18 months left on the deal he signed when he ed from Real Madrid in 2022.

He plays in flashes now but retains the nous which made him such a useful ally for Cristiano Ronaldo and Luka Modric in their Champions League-winning pomp.

Though the penalty area was packed, Casemiro was the first to react to his own header bouncing back off both posts for his second. He might even have had a hat-trick but skied an injury-time chance over the bar to leave Van Nistelrooy with his head in his hands.

If the VAR system had been in operation, as it will be when these sides meet in this stadium in the Premier League on 10 November, the home side’s second goal may not have stood.

Dalot looked offside as he collected Casemiro’s down the touchline. Leicester boss Steve Cooper certainly thought so, and by a long way, judging by the gesture he made as he complained to the officials.

The flag stayed down – as VAR protocol dictates. But for this game, there is no VAR as the EFL feel it could create an imbalance as it is not used at grounds in their league competition.

Instead, it is reserved for the Wembley final and the semi-finals, so Dalot carried on with his run and crossed low across the six-yard box, where Garnacho strode onto the ball and drove home at the far post.

Cooper was livid, earned a booking for his protests and is now banned from the dugout for Saturday’s crucial trip to Ipswich.

The goal effectively took the game away from a Leicester side showing nine changes from the team beaten at home by Nottingham Forest last week.

There were moments when Cooper’s side looked ok and El Khannouss’ first Leicester goal was a noteworthy effort as he cut across his shot with the top of his boot and sent it low into the bottom corner.

Cooper knows the main demand of this season is not emulating the Foxes’ previous triumphs in this tournament. His task is to keep them in the Premier League, and Saturday’s game at Ipswich is huge.