Sir Alex Ferguson has admitted their recent 4-4 draw with Everton could prove to be the 'killer' moment in their Premier League title quest.
Had United held onto their 4-2 lead over the Merseysiders in the closing stages a fortnight ago, they would have gone into Monday's Manchester derby five points clear of City, providing an adequate buffer against the 1-0 defeat they suffered.
Now they trail on goal difference and require either improbably high wins against Swansea on Sunday or Sunderland next week, or a massive favour from one of City's final two opponents - Newcastle and QPR - to give them a reprieve.
If it does not come, Ferguson has already pinpointed where it all went wrong.
"The Everton game was a killer for us," the Scot said.
"It was a ridiculous performance from us in the last 10 minutes of a match. We were absolutely careless.
"It's all right saying that in the history of our club we tend to attack all the time, but that was a stupid performance and it's put us on the back foot.
"We'll have to accept that if we lose the league it was the Everton game that did it - absolutely no doubt about that."
City have an impressive record on Tyneside but Newcastle have maintained an impressive level of performance under manager Alan Pardew throughout the season, and in 13-goal striker Papiss Cisse have one of the best buys of recent times.
As a former striker himself, Ferguson could not help but be impressed by the Senegal international's double in the 2-0 win at Chelsea on Wednesday, although he did believe the first effort was the best.
"It was incredible," he said. "People are going on about the second goal but the first goal was the better one.
"He had to take a touch on it and from the angle he was at to put it in the top corner was fantastic.
"The second goal could have gone anywhere, although it was an incredible hit."