Ashley Young's needless dismissal and Chris Smalling's farcical own goal sent Manchester United crashing to a damaging 2-1 defeat against Wolves on Tuesday.
Ole Gunnar Solskjaer's side blew a chance to move into third place in the Premier League as they squandered the lead in a disappointing display at Molineux.
United remain fifth, but their hopes of qualifying for the Champions League via a top-four finish will be further dented if Tottenham and Chelsea win on Wednesday.
It was a frustrating night for Solskjaer, who saw United suffer a third defeat in their last four games — underlining how much work the Norwegian still has in front of him following his appointment as permanent manager last week.
Scott McTominay's first goal for United was negated by Diogo Jota before the interval, but the game's turning point proved to be a second yellow card collected by Young with just 57 minutes gone.
United finally caved to Wolves' pressure 20 minutes later, when Raul Jimenez rose above Phil Jones and headed a Joao Moutinho cross goalwards.
The awkward attempt saw Smalling and goalkeeper David de Gea become entangled, with the former making the final touch as the ball rolled over the line.
‘No margin for error’
Ole Gunnar Solskjaer admitted Manchester United have no further margin for error in their bid to secure a top-four finish after a damaging 2-1 defeat against Wolves.
United had been set a target of 15 points from their remaining seven games by the manager before their visit to Molineux.
That total is now 15 points from six matches, with games to come against both Manchester City and Chelsea at Old Trafford, a target which Solskjaer admits leaves no room for mistakes.
"I'm as confident as I was three hours ago," joked Solskjaer after the defeat.
"I said we need 15 points from our last seven games and now we need 15 from our last six.
"It's difficult but then again, we're a very good team and it's going to be difficult for anybody who plays against us.
"This was a tough game but a performance that deserved a win."
The game's turning point proved to be a second yellow card collected by Young with just 57 minutes gone.
Young was booked twice in the space of five minutes for fouls on Jota, the second a particularly unpleasant high challenge.
"When you're on a yellow you're always in danger of it being a yellow card again," said Solskjaer.
"Probably it was a bad decision by Ashley but in the heat of the moment he reached for the ball and was a little bit too high, it made it more difficult.
"We didn't get the pressure built that we expected, so we kept possession well but then they scored with the first chance they put the ball in the box."