The FCB official believes that a loss in Wednesday's match will severely damage his side's title aspirations, while Heynckes did not give as much importance to the upcoming game
The Bavarian giants are three points behind BVB ahead of the match at the Westfalenstadion, and Rummenigge concedes that a negative result may throw his side out of the race for the Bundesliga title.
"We cannot lose because that would probably decide the championship early," he told the club's official website
"In the event of a draw, the race would still be open, and with a win we would be in pole position to take over the lead Dortmund enjoy at the moment."
Meanwhile, Bayern coach Jupp Heynckes refused to rule out his club's chances even in the event of a loss.
"Only after the last day will we know who wins the title," Heynckes noted. "It will still be open after Wednesday.
"I am looking forward to a great game for the fans."