Bayern Munich can make a fool of you. Ask Niko Kovac.
How, for instance, did he lead Bayern to a 5-1 defeat against Eintracht Frankfurt back in November?
Kovac, who was head coach of Frankfurt before landing the Bayern job, cleared his desk at Sabener Strasse shortly after that aberration and would have been forgiven for giving Saturday's rematch a swerve.
What he missed in the battle of his former teams was a sometimes confusing 90 minutes, and further proof that Bayern can make one feel a fool.
At the 50-minute mark, they looked an unstoppable force, 3-0 to the good against a Frankfurt side who had lost four Bundesliga games in a row before arriving at the Allianz Arena.
Leon Goretzka, Thomas Muller and Robert Lewandowski punished increasingly feeble defending, and Bayern were rampant. It would have been easy to lionise them at that point.
Tuesday's Klassiker clash with Borussia Dortmund looked like a fixture they could tackle without any questions asked over their levels since the league resumed.
Enter Frankfurt's Martin Hinteregger, whose most memorable involvement to that point had been landing an accidental blow that caught Lewandowski near the eye.
In the space of three minutes, he twice embarrassed Bayern's defence, first when allowed far too much space on the edge of the six-yard box to bundle beyond Manuel Neuer, and then when he jumped between a gang of red shirts to head home a corner.
Game on? Not really. Order was restored as Alphonso Davies danced through a dithering Frankfurt defence for a gift of a fourth Bayern goal.
And then came another reminder of how Bayern can make even a towering footballer cringe, as Hinteregger made it onto the scoresheet for the third time in the half, albeit this time at the wrong end.
Attempting some clever footwork to fend off another Bayern raid, he contrived to trickle the ball into an empty net with some of the ditsiest defending seen this side of Djimi Traore.
Bayern finished up with five goals and have beaten Frankfurt 11 times in a row at home now, while Eintracht have now lost 10 of 13 away games in the Bundesliga this term.
Their coach, Adi Hutter, had the bragging rights in November but might now be fearing for his job.
Dortmund will analyse Bayern's performance and search for conclusions, noting those moments of vulnerability that Frankfurt exploited. There were weaknesses to be found, but it would not seem prudent to read too much into those.
The logical conclusion is that Bayern switched off, believing the game to be already won, and will be far more wary of Dortmund from the first to the last whistle at Signal Iduna Park.
So four points separate the top two again, with the Hansi Flick revolution at Bayern still sweeping all aside in Germany, regardless of the odd bump in the road.
Dortmund might take some heart from the cracks in Bayern's backline, but equally Muller and Lewandowski looked primed to exploit any weakness in any side, any day of the week. Tuesday? They can do Tuesday.
Five goals and a mid-match nap was not a bad primer for the biggest match of the Bundesliga season.