Rummenigge concerned for struggling Bayern
Bayern Munich coach Louis van Gaal is coming under growing pressure after the club's worst start to a Bundesliga season in 43 years.
A 2-1 defeat to Mainz left the record German champions languishing near the foot at the table with just two points from their first three games of the season.
Even Van Gaal's predecessor Jurgen Klinsmann, who was sacked after 10 months in charge last season, managed to win at the third attempt.
Next weekend sees Bayern face defending Bundesliga champions Wolfsburg.
"It is very serious,'' admitted chairman Karl-Heinz Rummenigge. "We have got to turn the corner and the next game is going to be very difficult.''
Wolfsburg were hoping to move seven points clear of Bayern at the top of the table by making it three wins out of three against Hamburg, but even the worst-case scenario would see them arrive at the Allianz Arena with a four-point cushion.
Rummenigge warned: "This is not a situation that we can be happy with. It is a dangerous situation which we must get out of as quickly as possible.''
Van Gaal made two substitutions before half-time, such was his disappointment with the 11 men he sent out onto the field.
Without the injured Franck Ribery, Bayern again lacked ideas and Miroslav Klose failed to do justice to his position behind Mario Gomez in the attack.
Van Gaal was unable to find an explanation for his side's poor form.
"I don't know what we have done wrong in pre-season,'' he said. "We are still looking for the right style of play for this team.
"We just cannot start games the way we started. It was very disappointing. That was a false start.
"We tried to put it right in the second half, but that is always too late in football. You have got to start from the first minute.''
While Bayern were left grimacing after another lacklustre performance, Mainz coach Thomas Tuchel was celebrating his first win as coach against arguably the most illustrious of opponents.
"I am incredibly proud of what my team did,'' Tuchel said.
Tuchel was appointed less than three weeks ago to replace Jorn Andersen, who had led Mainz to promotion to the Bundesliga last season.
But in those three weeks, he has made himself as much a cult figure at the club as Jurgen Klopp, who left last year after two successful decades as a player and coach.
According to general manager Christian Heidel, Tuchel has already done more than any of his predecessors managed.
"What Thomas Tuchel did tactically today is the best here in 20 years,'' Heidel said.