The war of words between the clubs rumbled on in the aftermatch of Bayern's 5-1 victory over Borussia Mönchengladbach on Saturday evening, with Uli Hoeness taking umbrage at comments made by Frankfurt's director of sport Fredi Bobic. In 2013 as he was set to retire for the first time, Bayern announced Pep Guardiola before the season was over and Heynckes bowed out in the best way possible - with a treble.
Without doubt the biggest losers of the managerial appointment, Eintracht Frankfurt have lost a promising manager that had transformed the club in a two-year spell.
However, that prompted an angry response from Frankfurt after sporting director Fredi Bobic, who claimed that the timing of the announcement was "unprofessional and lacking in respect" and could be damaging to the team's form over the remainder of the season.
"We thought long and hard about when to tell Frankfurt".
Bayern Munich have hit back in the war of words with Eintracht Frankfurt over the signing of coach Niko Kovac.
Bayern clinched a sixth successive Bundesliga last weekend and were on Friday drawn against Real Madrid in the semi-finals of the Champions League.
Kovač has guided his Eintracht Frankfurt side to within touching distance of a place in the Champions League next season.
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However, West Brom pulled out of the deal at the last minute when they made a decision to loan Gregorz Krychowiak from PSG. They have dropped a league-high 26 points from winning positions this season.
"When we realised in a final, final conversation that he was not doing it, we were talking to the coach, who was free, Thomas Tuchel".
Frankfurt now lie in 6th place in the Bundesliga, five points away from Champions League qualification, with four games to go.
Leverkusen stay fourth in the Bundesliga, now five points ahead of their opponents as well as Hoffenheim, who moved above Frankfurt on goal difference after first-half goals from Serge Gnabry and Adam Szalai gave them a 2-0 win against struggling Hamburg.
Former Croatia captain and boss Kovac played for Bayern from 2001 to 2003. "We are convinced that he is the right coach for the future of FC Bayern".
However, according to reports in January, the Colombian would look to leave Bayern if Heynckes were not to extend his own deal and manage next season.
The 46-year-old will start a three-year contract with Bayern from July 1.