First, after just 15 minutes, West Ham forward Sofiane Feghouli was shown a straight red card when a booking seemed sufficient. An already defensive home side retreated even further and substitute Juan Mata broke the deadlock just past the hour-mark.
Then, to compound the misery, Zlatan Ibrahimovic was clearly offside when he slammed home the away side’s second to wrap up the victory 12 minutes from time.
But Mourinho, ever the pragmatist, decided against discussing those two key moments, and even intimated that playing 11 v 10 was more difficult for his side.
When asked whether it was nice for key decisions to go his way, he replied: “Which decisions? To bring on Mata at half time and [Marcus] Rashford later. Thank you, thank you very much.”
He went on: “No. When I play at home I have in my office all the details. At half time I can watch and after the match I can watch immediately. When I play away I don’t have access to that so I cannot comment on that decision.
“I think it was not a very good performance. I think it is very difficult to play football in these circumstances, within 48 hours [of the last game].
“It’s not just hard for a team with 10, but also a team with 11.
“When you have one player more you have to think very well and they were too tired to think well. When you are fresh you play simple. When you are not fresh you play complicated.
“Only when I brought fresh people, Mata, Rashford, the team was different. We gave width with Rashford. We gave an extra body in the creation area so I think we deserved to win.”
East London can be an unforgiving place at the best of times so you can be sure that Dean and his assistant referees will not be welcomed back for a while. The vast majority of the club-record 56,995 crowd could not believe the flash of red following Feghouli’s foul on Phil Jones.
The Algerian had lost control of the ball with a poor touch and, on the stretch, he had left the England defender in a heap. But Dean’s decision that the challenge warranted an early, game-changing dismissal received a collective gasp of disbelief.
The red card meant West Ham’s desire to attack diminished even further which allowed United to control possession, although they failed to create a chance until the 36th minute, when they somehow squandered two inside a second.
Henrikh Mkhitaryan’s low cross looked certain to be turned home by Antonio Valencia but his effort was saved by Darren Randolph, who then gleefully snatched the ball off the line when Jesse Lingard inexplicably tapped the rebound onto the post from close range.
Mourinho attempted to turn the screw at half-time by replacing Matteo Darmian with Mata but it was the 10 men of West Ham who created the better chances early in the second half with Antonio wasting two good chances.
First he rose like a salmon but headed it like one from Dimitri’s Payet’s free-kick then he beat the offside trap and raced onto Manuel Lanzini’s through-ball only to be denied by David De Gea when one-on-one.
They were punished for the misses in the 63rd minute when Mata made the break through.
Fellow substitute Rashford created it, wriggling to the byline before cutting back to the Spaniard, who steered a fine finish beyond Randolph.
Mourinho added: “I have to be honest, if Antonio scores I don’t think we win the game because when you are tired and losing it’s even more difficult.” Bilic responded by throwing on Andy Carroll in the 69th minute but, curiously, the one-man header machine replaced arguably the best crosser in the league in Payet.
And the Hammers fell further behind 12 minutes from time when the offside Ibrahimovic finished from just inside the area when Pedro Obiang’s clearance crashed into Ander Herrera.
Bilic, unsurprisingly, could not believe Dean’s decision to send off Feghouli. He said: “I wouldn’t have been happy with a yellow.
“If it was a yellow I would say ‘why a yellow so early in the game for basically nothing?’.
“The more times I’ve seen it, it’s the other way round: it was Jones who made more dangerous tackle than Feghouli.
“Jones made a scissor, that was dangerous, his reaction was to save himself.” On the offside goal, Bilic added: “To boost the frustration came the second goal which is a clear offside.
“Your whole season, your job depends on one or two decisions because the second one is a clear offside.”
Randolph 6; Nordtveit 5, Reid 6, Ogbonna 6, Cresswell 6;
Kouyate 6 (Fernandes 82), Obiang 5; Feghouli 5, Lanzini 7 (Ayew 89), Payet 5 (Carroll 69); Antonio 6.
Adrian, Noble, Fletcher, Quina.
De Gea 7; Valencia 6, Jones 6, Rojo 6, Darmian 6 (Mata 46); Pogba 7, Herrera 7, Carrick 6; Lingard 6 (Rashford 58 7), Ibrahimovic 7, Mkhitaryan 6 (Smalling 65 6).
Romero, Martial, Young, Fellaini.
Mike Dean Att: 56,996