Yet more injuries — this time to Luke Shaw and Eric Bailly — leaves United facing Thursday’s Europa League semi-final first leg at Celta Vigo without seven front-line first team players, four of them central defenders.
Just as damaging, the loss of two more points severely harms United’s hopes of a top four finish and a guaranteed place in next season’s Champions League.
But spare a thought for his opposite number Paul Clement who, quite rightly, pointed to a highly controversial first half Wayne Rooney penalty as the only thing that stood between his team and three priceless points in their bid for Premier League survival.
Deep in first-half injury-time, Marcus Rashford went down under a challenge from goalkeeper Lukasz Fabianski, presenting Rooney with the chance to coolly stroke in his first home league goal of the season.
Clement stopped short of accusing United’s England striker of cheating referee Neil Swarbrick into the award, but only just.
“I’m not saying he cheated, I’m using the word ‘deceived,’” said Clement. “Maybe cheat is a word I’d use another time but on this occasion I think he deceived the ref.
“I looked at the reaction of my players at the time and they were furious so that puts doubt in your mind. And also there was a delay between the contact — or non-contact — and the decision being given.
“The replay showed the player deceived the referee, there’s no other way to look at it. You can say he dangled his leg to make contact but he actually went down before that. The keeper pulled out of it.”
Clement saw justice done 12 minutes from time when Rooney made a tired and lazy challenge on Jordan Ayew presenting Gylfi Sigurdsson with the opportunity to chance his arm from a 25-yard free-kick.
The home defence spent an age organising themselves but that still did not stop the Icelandic international from stroking home a sublime equaliser which left David De Gea rooted to the spot.
There was even a last chance for a dramatic Swansea winner, in the 91st minute, although Fernando Llorente completely miskicked after Sigurdsson’s free-kick found him just six yards out.
By then, Mourinho was already resigned to heading to Spain this week with yet more injury concerns after Shaw lasted just seven minutes before coming off with what looked like an ankle injury and Bailly was lost on the hour with an apparent hamstring problem.
“We lost players and we lost points, so yes today was a bad day,” said Mourinho. “We did not look tired and exhausted, we are tired and exhausted.
“You cannot isolate the performance out of the context. This is the ninth match of April, it is not human. We have a squad of 22 that is reduced to 13 or 14 players. The players are very tired.
“I don’t know about the injuries. I think Luke Shaw’s must be a big injury, because to leave the pitch after 10 minutes I am expecting a very big injury.
“We will give everything on Thursday. That is sure. Whether we go to the final or not doesn’t matter, I am really happy with the guys.”
It had been obvious from kick-off that United’s gruelling season had finally caught up with them. This was their 57th game of the campaign, 19 more than Swansea.
Llorente beat Bailly far too easily early on and tested De Gea and although Fabianski was required to save shots from Jesse Lingard and Anthony Martial, Swansea were strongly in contention.
Rooney should have carved out a second early after the restart but hit team-mate Martial from eight yards and while Fabianski was again tested by Martial and Antonio Valencia, Swansea looked just as likely to score as their hosts.
So it proved with the late drama and, as Mourinho picks up the pieces from yet another anti-climax at Old Trafford, one alarming fact should be apparent. As things currently stand, United are on course for a fifth-placed finish and another season of strenuous, exhausting fixtures in the Europa League.
You voted this man as your Man of the Match today. Well deserved, Gylfi! 👏 pic.twitter.com/SxKK8OsMjc— Swansea City AFC (@SwansOfficial) April 30, 2017
De Gea 6; Young 7, Bailly 6 (Darmian 60, 6), Blind 7, Shaw (Valencia 8, 7); Carrick 6, Herrera 6; Lingard 7, Rooney 6 (Mkhitaryan 80, 6), Martial 6; Rashford 5.
Subs (not used) Mata, Romero, Tuanzebe, McTominay.
Fabianski 7; Naughton 5, Fernandez 7, Mawson 7, Kingsley 6; Ki Sung-Yeung 7 (Fer 60, 6), Britton 7 (Montero 66, Olsson 72, 6), Carroll 6; Ayew 7, Llorente 7, Sigurdsson 9.
Subs (not used) Amat, Boston, Nordfeldt, Cork.
N Swarbrick (Preston) 6