The German midfielder has signed a contract extension until 2026 and is currently attracting interest from top clubs such as Manchester City and Liverpool.
Hainer said: "We love Jamal Musiala, and it is clear that he is the kind of player who appears once in a century.
"It is clear that our main task is to extend his contract and keep him at Bayern for a long time."
In total, he has 46 goals and 34 assists in 169 competitive matches for the German giants.