Bayer Leverkusen have warned Michael Ballack's agent that he may never step foot in their stadium again.
It follows a feud between the club and the former Chelsea midfielder's representative over Leverkusen's treatment of Ballack.
Dr. Michael Becker believes that Ballack has been treated like a 'pawn' at the club, having struggled to hold down a regular place in the team.
Becker met with the club's director of sport Rudi Voller this week to resolve the issue, following managing director Wolfgang Holzhauser's comments suggesting that the transfer had not worked out.
Voller said: "It is the duty of Michael Ballack to represent his own point of view in disputes, but not via his agent.
"He should stop attacking us as a club.
"He has been shown the yellow card, this is the last time he will attack us in this manner.
"That will never happen again or he will never set foot in the stadium again."
Leverkusen are sixth in the Bundesliga and aiming for a European place at the end of the season, but they have to overcome a nine-point difference between themselves and fourth-placed Borussia Monchengladbach.
Ballack is set to leave the club when his contract comes to an end in the summer.
Voller added: "We want to have a successful second phase of the season. Therefore we need Michael Ballack on the top of his game.
"Signing him (in 2010) was the right decision. I had expected to see Michael Ballack doing duties that he has not shown; expectations that he has not fulfilled."