Bayern Munich legend Uli Hoeness regards RB Leipzig as a "dangerous opponent" and believes Red Bull owner Dietrich Mateschitz will further invest in the transfer market in January.
Leipzig remain unbeaten after nine games of their debut Bundesliga season and lie only two points behind Bayern in second place in the table.
"I honestly must say, Red Bull Leipzig are very strong," Hoeness, a former Bayern player, general manager and president, told Sky Deutschland. "Of course, in my opinion, they have the advantage of lying on the sofa during the week when we are in Champions League rhythm."
Leipzig were only formed in 2009 and have made a meteoric rise through the leagues with energy drink giant Red Bull's backing.
Commenting on Bayern's nearest challengers' financial power, Hoeness added: "If I know Mr Mateschitz correctly, he'll stump up a few more million at Christmas time if needed. In this respect, Leipzig is medium-term a dangerous opponent."
Leipzig have made the best ever start by a promoted side in Bundesliga history and the current top two meet in the last game before the winter break on Dec. 21 in Munich.
Hoeness, Bayern president between 2009 and 2014, was released from prison in February after serving 21 months for tax evasion. He is expected to be re-elected unopposed into the role for another term at the club's AGM on Nov. 25 in Munich.