Since Heynckes replaced Carlo Ancelotti as head coach at the start of October, Bayern have won 22 of 23 matches going into Tuesday's clash at Munich's Allianz Arena.
Bayern were five points adrift of then-leaders Borussia Dortmund in the Bundesliga when the 72-year-old Heynckes returned for his fourth stint at the club.
A 3-0 thrashing at Paris Saint-Germain in late September was Ancelotti's final game before Bayern turned to Heynckes to fix the leaks.
It was a gamble.
Tending the garden and walking his dog Cando had been Heynckes's main tasks since steering Bayern to a treble of Champions League, Bundesliga and German Cup titles five years ago.
"My wife and my daughter said I should do it," said Heynckes when Bayern came calling again.
"My dog also barked twice, so that meant I should do it."
Training started an hour earlier, sessions were tougher and discipline was tightened under Heynckes.
Thomas Mueller, a player Ancelotti never figured out where best to position, was moved in from the wing and deployed to roam just behind striker Robert Lewandowski.
Javi Martinez was pushed forward from centre-back into defensive midfield, where he played in the 2013 campaign, and the impact was instant.
Bayern won 5-0 at Freiburg in Heynckes's first game back.
"No one could have known what four years away from football had done to Jupp," said Martinez.
"Now I know: he’s stayed the same. He still has his personality - he always knows exactly when to tighten the reins."
Bayern were back in business and won their next nine games on the trot.
A 2-1 defeat at Borussia Moenchengladbach in November remains their only reverse following Heynckes's return.
They reached the German Cup semi-finals the hard way after winning at RB Leipzig and Borussia Dortmund in the early rounds.
Then in December, the humiliating defeat in Paris was avenged when Bayern beat PSG 3-1 in Munich - although it wasn't enough to prevent them finishing second in their Champions League group.
The Bavarians have also regained their unyielding grip on first place in Germany, with Saturday's 2-1 come-from-behind win at Wolfsburg leaving them 19 points clear at the summit.
Resting several stars, Bayern fell behind after eight minutes, but their drive and determination was rewarded as Lewandowski came off the bench to net a last-gasp penalty for his 20th league goal this season.
"This will to win matches, even if it's not so exciting at the top (of the table), just makes it fun," said Bayern captain Mueller. "This team is simply awesome."
Just like Mueller and Martinez, the other leading protagonists from the great 2012-13 side credit Heynckes for the club's rejuvenation.
Robben helped create both goals at Wolfsburg, whipping in a cross for Sandro Wagner and then winning the penalty which Lewandowski converted.
"You could see the turnaround from the first day," said Robben, who scored the winning goal in the 2013 Champions League final.
Franck Ribery's recovery from a knee injury has also helped, with the Frenchman on target in wins over Bayer Leverkusen and Mainz since the turn of the year.
"We're playing as a team again - with Jupp's return, a good feeling and the faith came flooding back," Ribery said in January.
It's not just the holdovers from the previous Heynckes era who have profited.
Colombian playmaker James Rodriguez has blossomed under Heynckes, a fluent Spanish speaker and the man who led Real Madrid to Champions League glory in 1998.
"This team won't let up, regardless of what competition it is," Heynckes warned.
But whether he is in charge beyond the end of this season remains doubtful, as Heynckes insists he will walk away despite efforts to persuade him to stay.