Ottmar Hitzfeld admits he had to set an example by punishing Bayern Munich captain Oliver Kahn.
The veteran goalkeeper has been fined 25,000 euros (£17,940) by the German giants, and suspended for the final Bundesliga game before the winter break against Hertha Berlin on Saturday.
The sanction was a result of Kahn's criticism of team-mates Luca Toni and Franck Ribery, and his early exit from the club's Christmas party.
Bayern coach Hitzfeld outlined his reasons for punishing Kahn, saying the 38-year-old should be a role model for the club's youngsters.
"I had to set an example so everyone at Bayern knows how they're expected to behave," Hitzfeld told a news conference.
"Players criticising their team-mates must stop. Otherwise we become a madhouse.
"Kahn must know he has to set an example to the younger players and at the Christmas party he did not behave well.
"The captain can't leave early."