Germany's Bundesliga is becoming the most fickle of Europe's major domestic championships.
Its titles, once seized, become as slippery as a wet bar of soap. Borussia Dortmund should feel warned. The 2011 championship already looks destined as theirs, but they should be wary of assuming their huge lead means that their success will endure.
Four days ago, Wolfsburg, the 2009 champions, sacked their English coach, Steve McClaren. He had lasted about six months in the job, which is near the average length of stay for coaches seeking to live up to the Wolves's heightened expectations. McClaren was the third manager there since Felix Magath guided Wolfsburg to the summit for the first time. They have since spent heavily to recapture that crown but sit, this weekend, in the bottom half of the table.
Bayern Munich, meanwhile, occupy fifth position, only a point beneath the zone that will get them into next season's Champions League but 15 points beneath Dortmund. For Bayern to retain their domestic crown, according to Karl-Heinz Rummenigge, the the club chairman, would require that "Dortmund commit suicide".
And as far as Rummenigge is concerned, there is only one team proving regularly expert in administering self-harm, and that is his own.
In the days since Bayern allowed a 2-0 lead at Cologne to turn into their fifth league defeat of the season, Rummenigge's has been the most conspicuous voice in laying down the law from the top of the club's hierarchy, where the major power-brokers are former Bayern players. Often, that role of headmaster is taken by Franz Beckenbauer, honorary president of the Bavarian club; sometimes the chastening opinions are left to Uli Hoeness, the general manager.
In times of crisis, a Bayern coach can feel that around every corner lurks a three-headed monster. At the moment, Louis van Gaal, the coach who led the club to the title and to the final of the European Cup in 2010, has a strong sense that crisis is imminent.
His minimum requirement is to have Bayern finish the campaign in the Champions League placings. His urgent need, as Rummenigge sternly told Bild-Zeitung, Germany's biggest newspaper, is to plug the leaks in Bayern's defence.
"Our problem is not up front," Rummenigge said, "because over the last few weeks we've been getting plenty of goals. We're dominant going forward.
"What we've got to do is stop the opposition getting so close to our goal."
His order for today's visit by Hoffenheim? "It's a must-win game."
The team's shaky morale has been easy to diagnose; Arjen Robben and Thomas Muller came to blows during the victory at Werder Bremen at the end of January. Failure to hold an advantage has become a recurring problem. Just as at Cologne, Bayern threw away a 2-0 lead in the Champions League when they lost to Roma.
Rummenigge may be consoled to know that, when it comes to holding out for the full match, Hoffenheim are as untrustworthy as Bayern. No team in the Bundesliga has conceded more goals in second-half injury time than they have.
B Munich v Hoffenheim 6.30pm
E Frankfurt v B Leverkusen 6.30pm
St Pauli v B M'gladbach 6.30pm
Schalke v Freiburg 6.30pm
Stuttgart v Nuremberg 6.30pm
Wolfsburg v Hamburg 6.30pm
Kaiserlautern v B Dortmund 9.30pm
Cologne v Mainz 6.30pm
W Bremen v Hannover 8.30pm
Team P W D L GD P
Borussia Dortmund 21 16 3 2 34 51
Bayer Leverkusen 21 11 6 4 13 39
Mainz 21 12 1 8 10 37
Hannover 21 12 1 8 -1 37
Bayern Munich 21 10 6 5 16 36
Freiburg 21 10 4 7 1 34
Hoffenheim 21 8 8 5 11 32
Hamburg 20 9 3 8 -1 30
Nuremburg 21 8 5 8 -4 29
E Frankfurt 21 8 3 10 -2 27
Schalke 21 7 5 9 0 26
Wolfsburg 21 5 8 8 -4 23
W Bremen 21 6 5 10 -16 23
Kaiserlautern 21 6 4 11 -6 22
St Pauli 20 6 4 10 -11 22
Cologne 21 6 4 11 -14 22
Stuttgart 21 5 4 12 -2 19
B M'gladbach 21 4 4 13 -22 16