Just over one year ago, Magath's VfL Wolfsburg team handed Bayern a humiliating 5-1 defeat which sent the Bavarians into freefall and put his own team on course for the title.
This time, Magath, who gives most of his news conferences drinking tea and dunking the bag into his cup, is threatening to destroy Bayern's hopes of winning a league, cup and Champions League treble by leading Schalke 04 to the title.
Schalke's last-gasp win at Hertha Berlin last Saturday pulled them level on points with Bayern at the top with two matches left to set up a nail-biting finale to the league.
Bayern still have the better goal difference but Schalke do not have any other commitments to distract them.
It is often felt that Magath - known as a tough disciplinarian who likes his teams to play on the counter-attack - has unfinished business with Bayern after they sacked him midway through the 2006/07 season, six months after he won the double for the second time in a row.
Known as Quaelix, a mixture of his first name and the German verb for to torture, Magath comes across as thoughtful and pensive in television appearances but is reputed to be a fearsome task master for his players.
MIND GAMES
Magath has already started playing mind games with his former club and coach Louis van Gaal.
"We have the more difficult run-in," he said. "But Bayern have not done so well against less strong teams. I think they will stumble.
"I'm sure that Bayern will not win both their final two games."
However, he played down any bad feelings with his former club. "I don't have a feud with Bayern. It's just that we have the same goal."
Schalke could not be further removed from their rivals in terms of personality.
While Bayern are regarded as Germany's most glamorous club, the Royal Blues are based in the industrial city of Gelsenkirchen where they have an almost cult-like following.
Their stadium is one of the most atmospheric in the Bundesliga and, packed with denim-clad fans, often harks back to the 1980s.
They won the last of their seven titles in 1958 but have been runners-up three times since 2001.
Schalke have a tough match on Saturday as they host third-placed Werder Bremen, the league's highest scoring team, while Bayern host relegation-threatened VfL Bochum.
Schalke then travel to Mainz for their final game the following weekend while Bayern are at bottom club Hertha, who may have been condemned to relegation by then.
Bayern, who face Werder Bremen in the Cup final on May 15, will have to contend with a wave of euphoria on Saturday, following their 3-0 win away to Olympique Lyon in their Champions League semi-final second leg last Tuesday.
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