The FCB supremo has laughed off suggestions that the Croatia international could be on the move this winter
Mandzukic was left out of the Bayern squad for their 2-0 Bundesliga win over Borussia Moinchengladbach on Friday after failing to impress in training, fuelling speculation that the 27-year-old could be leave FCB this winter.
"I have heard that Mario did not train very well," the Bayern president told Sky.
"I really hope that he will improve in the next few weeks. We need Mario Mandzukic this season.
"We have a number of important games coming up and it would be very unwise if we were to approach this important period without Mario."
Mandzukic has netted 10 goals in 16 Bundesliga appearances so far this season.
The striker has a contract with Bayern until the summer of 2016.