Isaac and Joelinton help Newcastle beat weakened Manchester United. Premier League

Manchester United are heading for the drop zone under Ruben Amorim, a head coach who took over on November 11 and forgot to pack the “bounce” often gifted to employers after sacking the last man in charge. This is United’s fourth consecutive defeat and after 11 matches the Portuguese coach’s record stands at six losses and four wins.

Peer in the table and Amorim’s team sit 14th with 22 points after taking the same number, 11, from nine league matches as they did under his predecessor Eric ten Hag. Once again the 3-4-3 formation failed and to see Joshua Zirkzee come off after half an hour was indicative of United’s disarray. Another development was the re-introduction of Marcus Rashford into the squad, with the forward saying he wanted a “new challenge”. If you can, get the head coach’s thinking on that.

It only took three minutes and 30 seconds for Amorim to sink his head into despair. Liquid from Newcastle, it was done amateurishly by United, who despite lining up their three centre-backs Matthijs de Ligt, Harry Maguire and Lisandro Martínez, allowed Alexander Isak, unmarked, to plumb the ball before Andre Onana’s goal. Allowed to do and proceed.

Maguire and Martínez were the main culprits as the in-form Swede split them to score his eighth goal in his last seven outings. Already, the men of Amorim were looking like a pub XI tumbling into the local park in the middle of a particularly enjoyable festive season. Nousair Mazraoui was his next opponent as Anthony Gordon’s dazzling pace slipped the right wing-back before the Newcastle winger beat Joelinton. He fired, but within moments Isak entered from the left side. The shot disappointed, could have been easily stopped.

Similarly, the striker also attempted to chip Onana after he had run clear of Bruno Guimarães’ 50-yard pass from close to his own area. This enraged Amorim at his backline and he felt even more frustrated when, again, Eddie Howe’s side scored easily.

This came thanks to a United midfield that was hot butter to Newcastle’s red-hot knives. Possession was worked wide to Gordon, he set the ball up, and Joelinton made the helpless Martínez look like a schoolboy by standing up and taking the second.

Amorim was to blame for the gaping hole as, with Manuel Ugarte and Bruno Fernandes unavailable, he took advantage of Kobi Manu’s silky offerings and the 19-year-old’s legs to send Casemiro and Christian Eriksen into battle on a combined 64. Had left. Newcastle’s powerful, fast trio of Joelinton, Sandro Tonali and Guimaraes.

Harry Maguire (left) scratches his head in disbelief at Old Trafford. Photograph: Phil Noble/Reuters

The visiting fans were delighted, taunting their hosts with a killer line from the Beach Boys’ sloop John B – “This is the best trip I’ve ever been on” – and soon they were cheering even louder. An effort from Tonali led to a corner and Kieran Trippier’s delivery came close to beating Onana from a set piece in the 2–0 upset against Wolves on Boxing Day. Also threatened in the follow-up, but not as much as Tonali, who hit a post moments later.

How could Amorim and his people feel worse? The 39-year-old’s selection in the decisive 32 minutes was so disappointing that Zirkzee should be dropped for the menu. He came in alongside Casemiro, with Eriksen replacing the disgraced Dutchman. Zirkzee went straight down the tunnel. United’s only hope was for Newcastle to concede: Fabian Schar sent the ball straight to Manu, his pass went to Casemiro and his chip-cross found no one. United returned the worst 45 minutes of Amorim’s brief tenure.

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The second part was a test for each manager. Can Howe maintain his team’s excellence? Can Amorim Plan a Revival? If given the chances the visitors would be four or five clear.

Rasmus Hjolund earned United’s first corner in the 51st minute, but Eriksen’s execution was as effective as Casemiro’s out-of-the-boot cross after it broke down. Still, it was brilliant from the hosts. Amad Diallo’s effort was parried and United exercised some control and tapped the ball in, at one stage culminating in Maguire’s diving header which rapped Martin Dubravka’s right-hand post.

Suddenly Old Trafford was a cauldron, United’s strength giving the faithful something to believe in. Amorim introduced Lenny Yoro and Alejandro Garnacho for Martínez and Casemiro, with Marcus Rashford still left as a spectator, Maguire took the armband. Yoro hit a header and raced past Antony for De Ligt. But, the bottom line: there is no emphasis or danger about United. Amorim is overseeing a dip.