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 range

The ball squirmed past Matt Turner at his near post

Casemiro celebrated passionately following his decisive strike

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

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.

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

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.

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.

Ten Hag was yelling at referee Chris Kavanagh as Rashford was using an agitated semaphore to communicate with teammates.

Every time Forest broke through, United looked exposed, but Nuno’s team’s final-quarter decision-making was far from ideal.

Early in the second half, Elanga passed Awoniyi, who saw Onana block his effort. Divock Origi then bullied his way past a few players before his shot was blocked.

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.

After Victor Lindelof was cautioned for a cruel foul on Elanga, Nuno replaced Origi with Callum Hudson-Odoi.

Rashford was racing wide after Fernandes’ ball found him, and suddenly Forest was struggling to deal with the United captain’s guile. Then Casemiro curled a shot slightly over.

However, Fernandes’ free kick in the 89th minute was stroked past Turner by Casemiro, who beat the goalkeeper at his near post.

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

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.