Jose Mourinho’s men did not just play with the handbrake on for the opening 80 minutes or so, they were almost in reverse gear, so shot-shy were the Reds until the final minutes of this last 16 second leg.
By then it was too late, after an inspired substitution by Vincenzo Montella in the 72nd minute turned the game in favour of the Spanish side who had shown more composure on the ball and more adventure in attack than United.
Montella sent on Wissam Ben Yedder to replace the wasteful Muriel in attack, and within six minutes the French striker had scored twice to end Mourinho’s dreams of a third Champions League trophy.
Even though Romelu Lukaku scored a late goal to set up a slim chance of a fantastic comeback, it was of little consolation as United crashed out of the biggest cup competition in the game.
And they have only themselves to blame. Having exceeded expectations with the way they blew Liverpool away in the opening 25 minutes last Saturday, they went back into their shell and started in a curiously cautious way, even though Mourinho had set out with largely the same team that beat Liverpool.
Marcus Rashford, who had caused chaos against Jurgen Klopp’s men from the left wing, was switched to the right in order to accommodate Alexis Sanchez on his favoured flank.
But it did no favours to either player, as the Chilean disappointed again, especially in a flat first-half, and Rashford struggled to recreate his scintillating goalscoring form from the weekend.
Sanchez gave the ball away in promising positions, chipping forward hopeful rather than penetrative passes, and failing to get past the last man.
When he finally got a sight of goal, close to the hour mark, his toe-poke was easily blocked.
And what of Rashford? Having been so devastating cutting in from the left, the young England forward was wasted on the right.
He hardly had a chance to get a clear run at defenders, and when he did get in good positions, too often his delivery failed to find a man in a red shirt.
It was the same from the corner quadrant, as his set-piece crosses were cleared by the first defender on most occasions.
He also tried his luck with long-range free-kicks, one saved comfortably by Sergio Rico and another curled high over the bar after an hour.
Even a switch of position with Sanchez after half-time failed to produce any immediate improvement.
United’s sparsity in front of goal could not be blamed on Lukaku, who did what he usually does, throwing his not inconsiderable weight around in order to turn half-chances into opportunities and shooting on sight, but rarely with success.
United’s one clear chance of the first hour fell to Marouane Fellaini, who won the ball 30 yards out and exchanged passes with Sanchez before firing a powerful shot that was too close to Sergio Rico to force more than a tip over the crossbar from the goalkeeper.
The Spaniards, on the other hand, played without fear and always looked comfortable, not least Steven N’Zonzi, who put in the sort of commanding performance in the middle of the park that Mourinho and United’s supporters must wish Paul Pogba would match.
The two rangy French midfielders are competing for a place in Didier Deschamps’ World Cup reckoning, and on current form, the former Blackburn and Stoke midfielder would walk into any side ahead of the expensive but underperforming Pogba, who was limited to another cameo appearance as substitute here.
One could not help thinking that if Seville had a better finisher than Muriel, they could have run up a comfortable lead, and so it proved when the Colombian was replaced by in the 72nd minute by Ben Yedder.
The Frenchman struck within two minutes to put Seville ahead with an invaluable away goal, leaving United needing to score twice. When he headed in against a flapping De Gea two minutes later, it was effectively game over.
Mourinho tried to up the ante, sending on Juan Mata and Anthony Martial, and Lukaku volleyed a late goal. But it was too little too late.
Once the handbrake had been applied so early, United struggled to get out of second gear and could not up their game to turn it around.
The recriminations at Old Trafford may be long and profound, as this third defeat in 52 home games under Mourinho have left United with only the FA Cup to play for this season.
And unless they up their game considerably on Saturday night, who would be surprised if Brighton were to cause another shock — and create another nightmare at the Theatre of Dreams.