Despite playing second fiddle to Manuel Almunia at Arsenal, Lehmann spurned the chance to move back to Borussia Dortmund last week, citing "personal reasons".
Kahn, who lost his place in the Germany team to Lehmann for the 2006 World Cup, told the Bild newspaper: "In the past it would have been unimaginable that a national-team goalkeeper would be on the bench for his club. That is a problem, and Jens knows it as well. It is a dangerous situation."
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