Even without feeling betrayed by players he persuaded Arsenal to spend fortunes upon, Arsene Wenger would have known that his next game down Gander Green Lane represents a banana skin.
Wenger, more than any foreigner, has grasped the allure, and been wary of potential down-to-earth humiliation in the English FA Cup.
His Gunners have won the Cup six times. Tomorrow they travel just 30km across London to face the minnows of Sutton United.
Sutton have played for 118 years, and never opposed a team as grand as Arsenal.
Arsenal have played minnows, but not on the artificial turf, the Fifa-approved 3G pitch, that part-timers Sutton call their own.
Monsieur Wenger has to gamble on which of his players are fit, in mind more than body, to adapt from supine surrender in Munich to withstanding whatever the non-leaguers throw at them. And whatever they feel in themselves after one of the worst performances of their lives.
Wenger hears the rumours that every Tom, Dick and Harry could do a better job than he is now doing at the Emirates. The latest press talk is that Juventus' Massimiliano Allegri is being lined up should Wenger leave the club he has spent 21 years building.
Allegri, 49, jokes that the English lessons might need some brushing up. Wenger, 67, seldom jokes. He takes every little thing about Arsenal personally.
It has been the club where he has grown, well, old.
He arrived there in October 1996 from Nagoya Grampus Eight, in Japan. He was bespectacled, studious, and was courted by David Dein, then the Arsenal vice-chairman.
Dein, who left the club 10 years ago, was one of very few English directors who looked abroad and saw that a revolution was needed on the fields of football. In a nutshell, Dein wanted Wenger to bring foreign players, foreign influence, foreign habits of diet, discipline and outlook to the game England invented, and England stagnated into biff-bang-wallop long ball.
Whatever happens over the next few months before Wenger and his club decide their respective futures, he really did change all that. Speak to him at any time over the past two decades and you would feel disdain for crude football, obsession with artistry.
Too artistic? By a mile, say the critics, many of whom have never managed a team at any level. Their whipping boy in the Arsenal line-up is Mesut Ozil.
Wenger, they say, is deluded by Ozil, beguiled by the sophistry of his touch but blind to the frailty of combative spirit in the German of Turkish descent.
Yes, Ozil is a World Cup winner. But that carries no weight in the trenches of Premier League or Champions League warfare, where temperament is as tested as talent.
He's too languid, too much the poster boy of Wenger's finery over fighting instinct.
This is not a direct comparison, because no two players, especially across different time spans, are alike, but when I think of Wenger's trust in Ozil my mind goes back to Dennis Bergkamp, and even to Thierry Henry.
Bergkamp was more than a touch of peripheral elegance. Arsenal had signed him the year before Wenger's arrival, but he had his detractors.
Even a football-blind man could see the finesse in Dennis, the ability to control at a touch a moving ball that might escape others in the hurly burly physicality of the contest. Wenger saw a player who, once coaxed out of his introvert nature, could and did become the hypnotic match winner.
With Henry, whom Wenger first coached as a boy at Monaco, the manager had similar faith, and very grand designs. Henry was an in, and often out, winger at Juventus when Wenger bought him for Arsenal in 1999.
He grew into, or was cajoled and then liberated into, the all-time highest goalscorer in Arsenal's history. Swift, sublime, but predatory, and persuaded by Wenger to run across the entire forward line where instinct and big game preparation took him.
Wenger indulges Ozil and Alexis Sanchez too much?
Sure he does, like he did Bergkamp and Henry.
On the levels that Wenger sees the game, he looks for skills that he could never attain himself as a player. And he looks beyond the philosophy that (still) infects English football, despite the fact that seven out of every 10 outfield player in every EPL line-up are now imported.
Of course, there is wastage, huge human wastage, in the Wenger school of thought. Tomorrow's Sutton opponents will probably include four players who came through the Arsenal academy, and were discarded.
Craig Eastmond, 26, played a handful of first team games for Arsenal before disappearing into non-league. Roarie Deacon, 25, Jeffrey Monakana, 23, and Jack Jebb, 21, were all Arsenal apprentices.
They reached the Under-18 team coached by Steve Bould, who now sits at Wenger's side as assistant coach. For whatever reason, they were let go.
These are the judgments that the manager signs off season after season. In two decades the numbers of schoolboys, English and foreign, who are out there wanting just one chance to prove Monsieur Wenger wrong must be in the hundreds.
As Wenger told reporters on Friday, judgment is a huge part of the game. He might get a nasty surprise by one of Arsenal's cast-offs down at Gander Green Lane, and though it is perhaps a long shot of Leicester City proportions, Sutton might pull off the shock of Wenger's lifetime.
That, for sure, would end his Arsenal career the way that the media hounds smell it coming.
The Arsenal manager reminded everyone that he has turned down many offers to leave the club before now. Barcelona, Paris Saint-Germain, Real Madrid (and yes, Bayern Munich) all tried to tempt him.
One of those, or maybe even the lapsed giants in Milan, might still covet a manager who for so long has put the club before everything, family included.
All he says is that he will be coaching next season "here or somewhere else". Looking broken on Wednesday, but defiant by Friday - if only some Arsenal players were made of the same stuff as the manager.