Manchester United extended their quietly compelling run of Premier League victories to six here with a stodgy, lopsided, but still oddly inevitable 2-0 defeat of West Ham United pegged out around two decisive moments.

Asked afterwards about decisions going his team’s way, José Mourinho offered a playful show of innocence, agreeing that his own decision to rejig his team’s attacking personnel had made the difference. This was only half the story. The real turning point here was a Mike Dean joint, the Premier League’s most theatrically exhibitionist referee choosing to send off Sofiane Feghouli with 15 minutes gone after a challenge with Phil Jones that saw both men tackle strongly for a loose ball.

With the match scoreless at half‑time, Mourinho took his own moment to intervene, demonstrating the muscle in this United squad by bringing on Juan Mata and then after nearly an hour Marcus Rashford, who combined for the opening goal. Zlatan Ibrahimovic’s second near the end, lashed in coming back from an offside position, continued his own sublime run of form, a 12th goal in 12 games that will no doubt once again have his critics, such as they are, eating their balls.

Slaven Bilic felt hard done by at the final whistle after a disciplined West Ham rearguard. But despite some obvious fatigue at the tail end of the festive thrash, United still looked like a team gathering momentum. Victory in a bitty game, 48 hours after their previous win against Middlesbrough, leaves them in sixth and playing here with a sense of strength in reserve.

There was a stodginess to the early exchanges on a chilly night in east London. West Ham brought the first waves of noise rolling around this vast, open, egg‑shaped bowl, Feghouli and Dimitri Payet putting Manuel Lanzini in space for a low shot that David de Gea plunged to palm wide.

With 15 minutes gone the key moment in the match arrived. Michail Antonio chested the ball back towards Feghouli, who stretched to reach the ball, as did Jones. No studs were raised. It looked like a hard but fair challenge, although Jones came off worse. The referee took his time and then flourished – the word is apt – a straight red card.

It was a poor decision in many ways, a needless intervention that skewed the entire night for players, TV viewers and the near 57,000 people inside the stadium. As mistakes go it was at least on a fittingly Olympian scale, in keeping with the hauteur of a referee whose sweeping gestures suggest each match he attends is a spectacle made up of three interlocking forces, Team A, Team B and Mike D.

The flow of possession switched immediately. Michael Carrick began to tick in midfield as West Ham fell back into a hard-pressing 4-3-2 shape. Mourinho had made five changes to his starting XI, with Anthony Martial replaced by Jesse Lingard. In theory the front line retained its balance of speed and mobility either side of Ibrahimovic but on this wide pitch and against a team down to 10, Martial’s absence seemed significant. Havard Nordtveit was a fill-in at right back but United barely troubled him in the first half.

They should still have scored with 34 minutes gone. Ibrahimovic played a crossfield pass to Henrikh Mkhitaryan. He found Antonio Valencia in the middle. His weak, scuffed shot was straight at Darren Randolph, who scooped it away on the line. The ball trickled to Lingard, who somehow managed to hit the post. On the touchline Mourinho whirled around in search of someone to share his disgust with before spotting the rest of his dugout 50 metres behind him in one of the bubbles of empty space left by jamming a football pitch into this borrowed stadium.

West Ham had their moments, Lanzini’s curling shot drawing another clawing save from De Gea. Half-time arrived accompanied by a chorus of Dean-related boos, only partly drowned out by a blast of jarring and irrelevant music from the deafening stadium PA. At which point Mourinho made the change that would prove decisive, bringing Carrick back into defence and sending on Mata to lurk usefully just behind Ibrahimovic.

For a while things continued to almost happen. Cheikhou Kouyaté escaped without a card after a horrible tackle on Mkhitaryan. Antonio almost got his head to Payet’s free-kick. With United dominant but lacking punch, Mourinho brought on Rashford for Lingaard to test that right side with some thrust coming in from the touchline.

The home team still fought gamely, Lanzini skittering forward to put Antonio in on goal with a lovely little through pass. De Gea saved with his legs, but Antonio had time and space to find a corner. He really should have scored.

West Ham were punished two minutes later with a goal made and scored by Mourinho’s two substitutes. Rashford ran at Nordtveit, beat him twice and laid back a neat pass for Mata. His finish was instant, drawing a roar of pent-up relief from the away supporters.

United were cruising now as West Ham’s energy levels sagged. Paul Pogba picked up a loose Payet pass and shot just wide. Andy Carroll entered finally to test United’s own rejigged back line. They held on and with 78 minutes gone Ibrahimovic spanked in the second. He was offside. Pogba was also offside and arguably obstructing the defence. It was a goal that summed up both West Ham’s night and United’s own sense of gathering conviction.