Bayer Leverkusen sporting director Rudi Voeller is threatening to ban Michael Ballack's agent from the Bundesliga club's stadium as relations between the two sides reached a new low.

Agent Michael Becker said his client is being made "a scapegoat'' to mask problems within the club "because it's clearly not possible to fire (coach) Robin Dutt at this time.''

Voeller, a former Germany player and coach, responded furiously to those claims on Thursday.

"He says he knows it all,'' Voeller said. "He can't attack the club that way. He's got a dark yellow card. Or he was in this stadium for the last time!''

The director suggests Ballack, a former Germany captain, "has a duty'' to speak for himself and not send Becker to do his talking.

Becker had been responding to comments made last week by Leverkusen managing director Wolfgang Holzhaeuser, who said Ballack's return to the club in 2010 from Chelsea had been a failure because the player had failed to live up to expectations.

Voeller criticized Holzhaeuser for the timing of his opinion, expressed in an interview with the Cologne Express newspaper.

"Under no circumstances would I have given the interview at this time, but it was too late to intervene,'' said Voeller said. "In any case it's two, three months too early to take stock now already.

"(Ballack's recruitment had been) more than correct and I do not regret it. But I expect him to conduct himself as he did when he was introduced to us. He can make demands, but in the end the coach always decides.''

Ballack's Leverkusen contract expires at the end of the season. The 35-year-old midfielder wants to play on for another one or two years "at a high level'' elsewhere.

Leverkusen hosts Barcelona in the last 16 of the Champions League on Feb. 14.

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