Ruben Amorim’s wish to “create some danger” flared at the start of each half, then faded, as Manchester United were suckerpunched by Jean‑Philippe Mateta’s second goal, on 89 minutes, that sealed a first defeat in four games.

United and Crystal Palace were becalmed in front of goal except for when the Eagles twice took advantage of the home side’s slipshod defending. Mateta’s finish was simple. Ismaïla Sarr received the ball from Adam Wharton, shrugged off a challenge near halfway and slid the ball to Daniel Muñoz. He ran forward and squared to the striker, who did not miss.

A delighted Oliver Glasner, the Palace manager, said: “The second goal is everything we are always talking about. “I am delighted that it started with Adam Wharton [on as a substitute] playing a great one‑touch pass. Really great to watch, big win and we stay humble and keep going.”

It followed André Onana’s leaden feet causing the Palace opener: the home goalkeeper failed to tip over Maxence Lacroix’s header from Eberechi Eze’s 64th-minute free‑kick: the ball smacked off the bar and Mateta steered in.

The desire for more attacking menace was behind Amorim’s refusal to select Rasmus Højlund or Joshua Zirkzee and deploy Kobbie Mainoo as a false No 9 – a first for the head coach. It failed, though you can see the reasoning, as Mainoo is a far better technician than Højlund or Zirkzee and, as the midfielder illustrated in last season’s FA Cup final, he has a nose for goal.

Amorim said: “We choose to play with Kobbie to use the characteristics of Kobbie, it’s nothing against Rasmus or Josh. Sometimes the team scores goals by creating situations, using the right characteristics. It doesn’t mean if you play with two strikers you are going to score more goals.”

In one fluid back-to-front move, Bruno Fernandes lifted the ball to a galloping Noussair Mazraoui. He passed to Mainoo in the area, the 19-year-old glided into a right-hand zone, twisted and crossed: Alejandro Garnacho’s shot yielded a corner that came to nothing. Then Mainoo went close when his eye for goal led to him clipping Dean Henderson’s right post with Palace’s keeper marooned.

So, too, was Onana when a bright Palace foray split United’s rearguard. Diogo Dalot admired rather than challenged for Tyrick Mitchell’s ball from the left and Muñoz should have scored but headed wide.

Kobbie Mainoo battles with Max Lacroix and Will Hughes
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Kobbie Mainoo was used as a false No 9 by Ruben Amorim but the move did not pay off. Photograph: Martin Rickett/PA
Amorim talked of wanting to “improve” how his side entered the opposition’s final third but, if United impressed in flashes, there is a greater problem defensively. It is an ongoing issue he needs to fix. For example Daichi Kamada was able slip in behind the home side unnoticed, be found by a teammate, and turn and set up Mitchell. The wing‑back’s effort flashed by Onana’s goal and Mateta was a fraction away from connecting and scoring with a header.

As a marauding attacking force United had faded. They awoke, briefly, to knit a few passes together along the left yet after the ball was rolled back to Lisandro Martínez he blazed high and over. When Onana clutched a smartly worked Palace free-kick, he threw the ball to Mazraoui, who careered down the right. Amad Diallo took over, spotted Fernandes cutting in, and the captain’s first-time shot missed by a slim margin.

There was more: this time at a United set piece, a curved delivery from Fernandes was met by Harry Maguire and Ugarte, sliding in, saw his effort well saved by Henderson.

This phase of the second half resembled the opening of the first period: United pressed but lacked teeth. A sweeping Martínez pass was pinged on a left to right diagonal to Diallo but he could not hit the target.

On the hour Glasner brought on Eze, who was not fit enough to start but vibrant enough to create the opener. The winger’s free-kick was aimed at Lacroix, Leny Yoro was seriously outjumped, the defender’s header beat the flailing Onana, bounced off the bar, and Mateta drove in.

With 20 minutes to go Højlund replaced Mainoo, and Zirkzee was introduced for Mazraoui. For this game, at least, the Mainoo experiment had failed.

Before that, Eze’s ability to body-swerve made Martínez look like a defender drafted in from United’s junior ranks and if the Eze had not been thrown, too, by his own trickery – falling over as he tried a repeat – Palace’s one might have become two.

Injury was added to the insult of Palace’s ascendancy when Martínez crumpled and needed to be carried off on a stretcher. It was reminiscent of a similar episode against West Ham in February last year, when the Argentinian sustained medial collateral ligament damage and was out for nearly two months. Afterwards, Amorim offered serious concern.

At the close Palace’s supporters were jubilant and Amorim, whose record stands at 19 games, eight wins and eight defeats, has to regroup his players once again.