"We are not yet playing the stuff of champions," the 72-year-old said sternly, noting Bayern had done well in the first half but also conceded three big chances.

Goalkeeper Sven Ulreich, understandingly, focussed on his own good performance, easily the best since he stepped in to deputise for Manuel Neuer at the start of the season.

"I'm happy that I was able to help the team today," the 26-year-old said.

A few metres away in the bowels of the Signal Iduna Park, Mats Hummels' mind was already turning to the prospect of a sixth consecutive league win.

"We wouldn't mind if things got boring [at the top of the table again]," he joked, "I'm not sure that will be the case though."

Of all those happy assessments, Robert Lewandowski's laconic take was by far the most pertinent.

"Today we played really good football," the Polish striker said.

Really good football. When were those three words last spoken about a Bayern performance? Certainly not this season. Maybe once or twice in the previous campaign, when the Reds beat RB Leipzig 3-0 just before Christmas.

Domestically, they had sought recourse to their arch-Bavarian ability to win games, by way of mentality and individual class, in lieu of truly convincing performances. Internationally, that formula necessarily fell short. But the invigorating trip to Westphalia offered the clearest sign yet Bayern can once more raise their game to a whole new level, the like of which was last seen when Pep Guardiola was in town.

They were sharp in possession and created numerical superiorities near the ball by constant movement, aggression in the tackle and efficiency in the box. They had, in other words, all the attributes of a quality side. "European world class," Joshua Kimmich put on his Instagram feed, partly in jest.

Dortmund, by their own admission, didn't warrant similar classification.

"We were not a top side today," coach Peter Bosz lamented. "Bayern were clearly superior, especially in the first half. We only ran after the ball and always got there too late. In the second half, we got closer and showed that we can [play]. It was a real game then."

The late rally comes as scant consolation, however. A horrific run of seven games with only one win in all competitions -- a 5-0 victory over third division Magdeburg -- has put the Black and Yellows on the verge of Champions League elimination and transformed their five-point lead over their southern rivals into a six point-deficit and a limp to third in the table.

Bosz's tweaked system offered a bit more protection at the back but the insecurity that permeates the heart of the defence, where Omer Toprak and Sokratis Papastathopoulos are simply not of the required standard, continues to cause havoc. Dortmund have conceded 12 goals in their last four Bundesliga games. Such porosity has not been seen at the Signal Iduna Park since 2005-06, at the tail-end of Bert van Marwijk's unhappy stint.

Until Bosz gets his defensive house in order, other Bundesliga sides will continue to be encouraged and play without fear. Borussia's impressive attacking line, too, look as if they're psychologically affected by the fragility at the back. The only positive outcome of a depressing evening is that the size of the challenge has become painfully clear. Club, supporters, team and coach need to pull a lot closer together to ensure they will qualify for the Champions League again, at a bare minimum.

Bayern, conversely, feel their form might still improve. The steady progress under Heynckes has notably come in the absence of Neuer, Thomas Muller and Franck Ribery; Jerome Boateng didn't feature either on Saturday night.

"Naturally, we will become better and stronger," Heynckes predicted, ominously.

The self-satisfied lethargy of the Carlo Ancelotti era has been shaken off, and the club's traditional, insatiable quest for perfection has returned. Bayern might not be the fully fledged red monster again that rivals far and near used to fear but on the evidence of Saturday night, they look as if they could be frightening once more.