It is a very nasty habit for Arsenal but one they just cannot shake - the slump in form when all looks to be going so well. Defeat to Chelsea on September 29 stopped what looked like a season of promise in its tracks. Optimism has drained into disquiet. A mass exodus of angry Arsenal fans immediately followed Ibrahim Afellay's clinching goal for Schalke. The low proportion of them that remained at the final whistle showered their team with boos. They have done that before. Many times now, in fact.
Three Premier League wins out of eight is a record to barely trouble the scorers when it comes to assessing title contenders. Defeat at Norwich was the type of inexplicable defeat that Arsenal have been all too prone to in the eight years since Arsene Wenger last led a championship-winning team.
Arsenal still expect to be in the Champions League knockout rounds, often an unhappy hunting ground but a success to reach in itself. They made that perennial more difficult than it should have been in suffering a first Champions League defeat at home to a non-English team since they moved to the Emirates Stadium, a run that stretches back to a loss to Inter Milan at Highbury in 2003. The Germans' organisation had held Arsenal at bay to the point of distraction before two clinical finishes took advantage of pitiful defending, both via the same predictable route.
Klaas-Jan Huntelaar's finish was as precise as we have come to expect from the Dutchman. That he was allowed to run through on goal was down to his springing of the offside trap. Steve Bould, manning the dugout while Arsene Wenger completed his Champions League touchline ban, will have winced. Such things did not happen in his playing days. Then again, Bould did not play alongside Andre Santos, the hapless Brazilian full-back whose latest lack of spatial awareness had played Huntelaar onside.
Santos is no full-back. In fact, a footballing position is yet to be invented for him. The Brazilian roadhog offers much in attack but a lack of positional sense let Jefferson Farfan escape down his flank a ridiculous number of times. Kieran Gibbs, it almost goes without saying, is injured. A player of promise is having his development damaged by a halting physiology and his team are suffering without him too since his stand-in is simply not good enough to play for Arsenal.
When Afellay completed Schalke's victory when steering in a low finish, the supply line was none other than Farfan, with Santos again in a different postcode to where he was supposed to be. Santos had actually nearly intercepted the ball to Farfan. He was only able to do so because he was running back from the no-man's land he had found himself in once more. His stumble over the ball completed a comedic evening of defending. Schalke's victory was secured.
It might actually have been worse. Benedikt Howedes should have scored early in the second half when Farfan had overlapped past Santos with ease. Arsenal were lucky that Howedes supplied a centre-back's finish to continue the theme of players finding themselves in positions they are ill-suited to. The first half might have finished with a Huntelaar goal too when Atsuto Uchida escaped down the flank where Santos was figuratively supposed to be after having failed on one of his attacking sorties. He did not falter with his second chance.
That Schalke were able to exploit the same weakness time and again said much for Arsenal's tactical make-up. An obvious breach had been made, yet little was done to fill it. Wenger's stubborn nature often results in mistakes being repeated to the point of them proving fatal. That pattern was repeated here.
To further compound an evening with few positives, there was little attacking quality to make up for that defence with its glaring faultline. Creativity was lacking throughout, with the previously sainted Santi Cazorla rendered anonymous by the hard work of Schalke's midfield. Roman Neustadter's holding of his position provided a wall that Arsenal rarely got through.
Twice Gervinho had far too long to think when he was played into open space. And that is not a good thing for the quixotic talents of Gervais Lombe Yao Kouassi, to give him his full name. Twice he dallied, was caught up, and then fell to the floor for want of something better to do. The second occasion saw him booked for simulation.
The experimentation with Gervinho as a line-leader still has the jury out, and they have very probably reached a negative verdict already. The evidence of his predecessor in that role suggests that Gervinho is no long-term successor to Robin van Persie. Wenger, whose stone-faced expression in the directors' box said much about his view of the evening, must surely know this, even if some excellent recent finishes are brought in mitigation.
At times, Arsenal appeared to be playing with no line-leader at all - a fashionable conceit for some other teams but surely not what Wenger had in mind when he put together his team-sheet and match strategy. By the time Olivier Giroud came on in the 76th minute - far too late - Schalke were pushing towards their winning of the game. And Giroud had hardly nailed the centre-forward's position during Saturday's nightmare on Carrow Road.
Absentee majority shareholder Stan Kroenke was actually here, ahead of what will likely prove to be a stormy shareholders' meeting on Thursday. Kroenke's main role this week may be as owner of St Louis Rams, due to play the New England Patriots at Wembley in an NFL regular season game, but he is sure to be heavily questioned about why Arsenal's progress has once again halted.
He will find himself answering questions that he tried his best to skirt around this time last year, since the problems remain much the same as before. Then, he told an unconvinced audience that Arsenal had "all the elements for success". To repeat that would be as unconvincing now as it was then, if not more so.