Manchester United paid the price for Ruben Amorim's two mistakes at Nottingham Forest and he knew it

The team in red in the top three of the Premier League and off to Wembley for a semi-final. That was Manchester United only two years ago.

Ruben Amorim was regularly vexed at the City Ground. With Nottingham Forest's time-wasting, with the referee and with his own players. United are 13th in the table and have 13 Premier League defeats now, one fewer than the 14 they suffered last season.

Nottingham Forest remain ten places better off than United in this remarkable season of theirs. They have also done the domestic double against United for the first time since 1991-92, Brian Clough's penultimate season in management. It took Forest fans less than a minute to air the first rendition of 'You're not famous anymore'.

Forest have the most clean sheets in the Premier League and United have a -4 goal difference. A fifth-minute goal was enough. Including the added time at the end of each half, Forest clung on for more than 90 minutes.

United resorted to sending Harry Maguire on up front and he had better chances than the two strikers they spent £108.5million on. Maguire was denied an equaliser with one of the last kicks by Murillo on the line. Diogo Dalot, another defender, hit the crossbar.

And so United remain incapable of winning successive league games this season. Only Fulham and Newcastle United have left the City Ground with three points yet United headed to the Trent confident of making waves.

The progressive performances and results against Real Sociedad, Arsenal and Leicester City will feel distant now. United can hardly lament the inordinate international break for halting their momentum in one of their worst seasons since they were relegated.

Amorim will bristle at the manner of the winner. Forest operate similarly to Nuno Espirito Santo's Wolves side six years ago and United developed Anthony Elanga into the counter-attacking whippersnapper he now is. The United Twitter account could not even bring themselves to mention Elanga's name after he broke the deadlock.

United were enterprising and often on the front foot. That was to be expected against such a reticent side as Forest that relies on breakaways. Only Elanga put his best forward first. The away-dayers in the Bridgford End applauded appreciatively when the United players approached them at full-time.

Forest were more streetwise, too. Bruno Fernandes and Casemiro both snapped. The latter vented at the referee over a harsh booking he never recovered from. Casemiro was hooked seconds after a final warning from referee Jarred Gillett following a dubious foul on Morgan Gibbs-White.

Gillett was lenient amid the gamesmanship of Forest captain Ryan Yates, who milked Casemiro's tackle and got him booked but cynically tripped Fernandes and avoided a booking. In an unusual show of restraint, Fernandes remained mum.

Amorim outstretched his arms in disbelief at the time Matz Sels took to take a second-half goal kick and that was after Gillett ordered him to. The United coach Andreas Georgson also approached the fourth official to vent. Sels never saw yellow. United were not wise to Forest's game at either end.

Amorim has made a handful of selection errors and there were two too many at Forest. Pushing Fernandes forward and back into the front three had a knock-on effect on Rasmus Hojlund, illogically dropped to the bench as Joshua Zirkzee started at the tip of the arrow.

Zirkzee has developed a borderline cult following among the United fanbase partly since Amorim recognised his skill set is suited to a withdrawn role. To renege on that 16 days after United last played - and when Hojlund scored - was inexplicable.

Amorim acknowledged that he had erred at the interval. Hojlund replaced Manuel Ugarte, Fernandes dropped back and so did Zirkzee. Hojlund won a corner inside the first two minutes and made a run into the channel that is beyond Zirkzee. With United still in need of a goal, Zirkzee was substituted in the 78th minute. Maguire was a more threatening striker than both.

Elanga ran two-thirds of the pitch to have his matchwinning shot. Alejandro Garnacho at least attempted to upend him. Patrick Dorgu and Noussair Mazraoui did not know whether to come or go and before they had ended their indecision the scoreboard had changed.

Mazraoui was mindful of Gibbs-White offering support on the overlap. Dorgu somehow slowed down in attempting to keep up with an opponent who was sprinting with the ball. Elanga only got four goals for United and none were as electric as his winner against them. It is difficult to recall him ever operating at such a pace during his 18 months in the United fold.

Casemiro offered Amorim an apology for an early errant pass yet mucked in to tackle Elanga the next time he charged into the United area. When Elanga collected the ball in line with his own goal line, Mazraoui was too overzealous and conceded a needless foul. Amorim did not conceal his frustration as he stormed back into the dugout.

Amorim used a stoppage to chat primarily with Fernandes and Diogo Dalot, the two squad members he leans on the most. He soon had Casemiro's ear again, having previously got a message across to his former Sporting charge Ugarte.

Onana and Amorim urged United to quicken their play in the first half, mindful Forest were settling. Amorim smacked his thighs in frustration over a ponderous switch to Dorgu, who then underhit a backward pass in the 52nd minute.

This was another night United went backwards. Forest are going forwards.