While David de Gea missed the trip to Norfolk to have a wisdom tooth removed, his Manchester United team-mates suffered the type of collective kick in the teeth that could leave a lingering ache. Deservedly vanquished by a fearless Norwich side, whom Sir Alex Ferguson argued had "played beyond themselves", they could scarcely board their plane home fast enough.
There was little time for post-mortems. Ferguson had to trust that this meek defeat was an aberration, or at least the type of curiously listless performance that could disfigure any season. But an urgent tonic was required, and the United manager sought one from the restoration of Wayne Rooney, whom he hoped would be fit enough to lead the attack in tomorrow night's (Tuesday) Champions League game at Galatasaray.
Rooney has suffered a bout of tonsillitis but trained yesterday to book his place on this morning's flight to Istanbul. If only United's ailments were simply medical, for at Carrow Road they also seemed strangely debilitated in their play.
Robin van Persie suffered comfortably his worst display in a United jersey, with strike partner Javier Hernandez equally anonymous, while Ryan Giggs - sacrilegious as it might be to say so - looked a diminished force at 38.
Ferguson did his best to shrug off the concerns, claiming: "It was a game in which you have to give Norwich lots of credit for working so hard. It was a really special effort. It just didn't happen for us, and we didn't get into the space behind them. Norwich put lots of men behind the ball and closed out all the space, meaning that we couldn't get our crosses in.
"Ashley Young improved that, but we should have put the ball in earlier. There are times when you have to recognise that the opposition have played beyond themselves."
The result was one that nobody, least of all United, saw coming. Norwich had registered just two league victories all season, not securing their first until October 20, and yet here they suffocated Ferguson's players in a never-ending swarm of yellow-and-green.
It was a famous win on this oft-forgotten corner of the corner map - one to be cherished, perhaps, just as dearly as the conquest of Bayern Munich 19 years ago.
It was a chastening ordeal for the United fans, mischievously depicted by the home crowd as a glory-chasing brigade from nearby Great Yarmouth. "From the Yarmouth boys no noise", came the cry at the final whistle.
The fact that the winner had been scored by Anthony Pilkington, an academy player at United in 2004, enhanced the satisfaction. The winger himself insisted that he felt no grievance towards his former club, whom he left to join Blackburn, but admitted he had been inspired by a near-miss against United before. Having miscued when clean through at Old Trafford last season, Pilkington was unerring this time with a fine looping header from Javier Garrido's cross.
"It was good to put those demons away," the 24 year-old said. "I missed a couple at United, but I redeemed myself."
Pilkington was in no doubt, though, that his alma mater would have the resilience to recover. "They have got a great squad, probably the best team in the league," he explained. "They will still probably go on to win the title, but for now it's all about us."
Norwich manager Chris Hughton, instrumental in creating 'Fortress Carrow Road' with three successive 1-0 home wins in the league, singled out John Ruddy for particular praise.
The goalkeeper was called up to the England squad last week and the composure he demonstrated here, in front of a watching Roy Hodgson, was self-evident. The poise and personality he showed in repeatedly thwarting strikers of the quality of Van Persie was enough for local disciples to erupt into a chorus of "England's No 1".
Hughton said: "What I've been most impressed with from John are his concentration levels. Here he made the right decisions about when to come for the ball, and when not to come. He was brave, getting in among bodies, and that's the mark of a really good goalkeeper.
"The England manager was here and that certainly wouldn't have done him any harm. Appearing at international level is a mark of where you are as a player, so that should give him a lift."
The fact that Hodgson was here at all was a signal of how far Norwich had advanced over the past month, in dispatching Arsenal, Stoke and now United.
Hughton has ironed out their defensive vulnerabilities to the point where they are no longer odds-on to spiral into a relegation scrap.
Courtesy of Pilkington's inspiration and the resolve of Ruddy, they prevailed in the face of all detractors. For a complacent United, the entire experience must have been about as pleasurable as De Gea's dental treatment.