IT might sound like a proper ‘glory, glory Man United’ moment – an 89th-minute winner to settle a tense FA Cup tie.

But the decisive goal from Casemiro had an element of bizarre fluke, after another horribly flat performance from Erik ten Hag’s side.

Casemiro headed the winner from close rangeCredit: Getty

The ball squirmed past Matt Turner at his near postCredit: PA

Casemiro celebrated passionately following his decisive strikeCredit: Getty

Casemiro was made to wait due to a VAR check before the winner was confirmed

Man Utd shaded the momentum of the game

A free-kick from Bruno Fernandes out by the left-hand touchline bounced in front of goal, Casemiro added the slightest of touches with his head and, after a lengthy VAR check for offside, Man Utd were limping into the quarter-finals.

At least they avoided the potential nightmare scenario of a second defeat at the City Ground in the space of two months and confirmation of a trophyless season.

But the bold ambitions of Sir Jim Ratcliffe, to “knock Manchester City and Liverpool off their perch” looked light years away here.

Sir Dave Brailsford, Ratcliffe’s sporting director, was here on the eve of his 15th birthday on Thursday, when he turns 60 – and if that sounds confusing, look at the date.

Brailsford is said to be preparing a summer clear-out of United’s staff and this was another performance which suggested a deadwood sale is on the horizon.

United were poor, their own salvation being that Forest were poorer still.

There was a proper Cup tie atmosphere at this famous old stadium but this was no old-school knock-out match – in the second half, there was more chance of falling asleep than being gripped by Cup fever.

After the debacle of Saturday’s home defeat by Fulham – which ended a five-match winning streak – Ten Hag opted for experience by benching the teenaged duo Kobbie Mainoo and Omari Forson, while Harry Maguire missed out through injury.

Casemiro was the match winner for Man Utd at Forest on Wednesday evening

Antony and Scott McTominay came in, along with Sofyan Amrabat as a makeshift left-back.

Before kick-off they were showing big-screen highlights of United’s Premier League defeat here two months ago, adding to the sense of trepidation for the visitors.

Yet Ten Hag’s men almost snatched a fourth-minute lead when a corner was played short and Bruno Fernandes fed Antony, who crashed a shot against the bar.

Soon after, Diogo Dalot’s centre presented McTominay with a free header eight yards out but he couldn’t steer his effort away from keeper Matt Turner.

Then McTominay teed up Rashford who blazed over.

While United enjoyed the best early chances, there was plenty of attacking menace from Forest, not least from Anthony Elanga, a man with a point to prove after being flogged by United last summer.

Taiwo Awoniyi, a serious threat through the middle, had an angled shot repelled by Andre Onana and there was plenty of sloppiness in United’s midfield, where rumours of Casemiro’s “legs going” were looking pretty accurate.

A McTominay header was pushed around the post from another Dalot centre but there were signs of frustration from the visitors.

Rashford was communicating with team-mates in an agitated semaphore and Ten Hag was kicking off at ref Chris Kavanagh.

United looked vulnerable every time Forest surged forward but the decision-making of Nuno’s men in the final third left plenty to be desired.

Early in the second half, Elanga fed Awoniyi, whose effort was pushed out by Onana, then Divock Origi powered his way past a couple of defenders and had a shot beaten away.

At this point the best contest was the one Rashford and Fernandes seemed to be having over which United player possessed the worst body language.

Dalot, the full-back who was United’s best attacking player, released Rashford who bounced off Murillo and Felipe, fell over, then waved his arms about some more.

Just as United appeared to be flat-lining, Fernandes curled one wide with the outside of his boot, then had another effort diverted wide by team-mate McTominay.

Forest were flagging now, with United beginning to exert some authority, yet in the absence of Rasmus Hojlund, there was no focal point to their attacks.

Antony was withdrawn to chants of “what a waste of money” – the soundtrack to the £86million Brazilian’s life, with Ten Hag sending on Amad Diallo in his place.

Victor Lindelof was booked for a cynical foul on Elanga before Nuno sent on Callum Hudson-Odoi in place of Origi.

Rashford blazed wide from a Fernandes pass, the United skipper’s guile now causing problems for Forest, then Casemiro sent a curler just over.

But in the 89th minute, Fernandes delivered a free-kick which Casemiro touched past Turner, beating the keeper at his near post.

There was a long check from VAR Michael Salisbury, as to whether the offside Raphael Varane was impeding a Forest defender but United survived it.

And survival is the height of Ten Hag’s ambitions right now.