Marcus Rashford, having been left out of the previous four matchday squads with his United future in question, returned to the bench but was not called upon by Amorim, even with his side struggling to threaten the visitors.

Newcastle’s fourth straight league win gave Eddie Howe his first league success at Old Trafford in eight attempts and lifted the Magpies to fifth in the table.

Having scored in the opening minute of their 4-0 win at Ipswich nine days ago and in the second minute of the 3-0 Boxing Day win over Aston Villa, Newcastle needed four minutes to find the net here.

Lewis Hall’s cross spooned up off Noussair Mazraoui’s outstretched leg and it was all too easy for Isak to get between Harry Maguire and Lisandro Martinez and head home, becoming the second Newcastle player to score in six consecutive Premier League games after Papiss Cisse in 2012.

United never settled, the ageing legs of Casemiro and Christian Eriksen unable to keep pace with Newcastle, who threatened again when Anthony Gordon skinned Mazraoui to cut inside, Joelinton flashing a shot wide.

A rare United attack in the 17th minute actually ended in a glorious chance for Newcastle. Joelinton dispossessed Eriksen on the edge of the Newcastle box and immediately launched the ball forward for Isak to run at goal, only for the Swede to get his finish all wrong as he tried to dink it over Andre Onana.

No matter, as Newcastle went 2-0 up in the 19th minute thanks to more feeble United defending, with Joelinton overpowering Martinez to head home Gordon’s cross from close range.

On the half-hour mark Isak rifled a shot into the net on the angle before the flag belatedly went up for an obvious offside and two minutes later Sandro Tonali somehow poked a shot on to a post when it looked easier to score, with United carved open once more.

Amorim acknowledged the mistake in his original selection as Joshua Zirkzee, who started in place of Fernandes, was hauled off in the 33rd minute to an ironic cheer from the Old Trafford crowd, replaced by Kobbie Mainoo.

United seemed lifted and Martinez found the run of Rasmus Hojlund, only for the Dane to shoot across the face of goal and wide.

In first-half stoppage time, a poor pass from Fabian Schar gifted United another chance, but Casemiro squandered it as he scooped the ball wide when he had time and space. United finished the first half without a shot on target and lucky the score-line was only 2-0.

They began the second half with more purpose, driving at Newcastle and building some pressure.

Mainoo saw a shot blocked before Maguire headed Diogo Dalot’s cross against a post just before the hour mark.

Alejandro Garnacho and Leny Yoro replaced Casemiro and Martinez, and Yoro headed narrowly wide from a corner in the 74th minute, but still United could not test their former goalkeeper Martin Dubravka as Rashford watched on from the touchline.