Die Roten's former boss admitted the defeat did not sit well with him, but tipped successor Pep Guardiola to turn things around.
The 68-year-old led the Bavarians to an unprecedented treble last season, only to watch on helplessly as his successor Pep Guardiola suffered defeat in his first competitive match in charge at Signal Iduna Park.
However, Heynckes stated he was not to downhearted at the setback and tipped the Spaniard to achieve further success following his 14 titles in four seasons at Barcelona.
"I barely managed a team which was that perfect and so focused to succeed," he told ZDF Sportstudio. "Of course I'm not amused [by the loss], these are still my guys.
"The team isn't that far from showing a top performance. Pep looks very good, is well-dressed and has a perfect team. What could possibly go wrong?"
Guardiola replaced Heynckes in the dugout after the latter's contract expired, but the German insists he has no regrets about walking away from the game.
"At some point you have to decide to retire, this is what I'm going to do now," Heynckes added. "It's important to stay cool with this atmosphere in football. I think I did that well.
"I will watch the start of the Bundesliga from the comfort of my living room now."