Kuranyi left during the interval of Saturday's World Cup qualifying win against Russia, a game for which he was not included in the 18-man squad drawn up by coach Joachim Low.

Low subsequently stated he would no longer consider the Schalke striker for his future squad selections, while Kuranyi showed his remorse at a press conference on Monday, admitting he had made a mistake.

Reports in Germany suggest that Kuranyi was subjected to taunts from fans at the Westfalenstadion, the home of Schalke's arch-rivals Borussia Dortmund, during the first half of Saturday's match which may have prompted his decision to leave.

Bierhoff sympathised with the striker, who admitted he was still struggling to come to terms with being left out of the Germany squad for the 2006 World Cup.

"I have seen a bit of what Kevin said and you can see how tough it has been for him," said Bierhoff.

"We can understand it, but not what he did against his team-mates. That, we cannot accept.

"I do hope he rediscovers the strength and performs well in Gelsenkirchen.

"He always seemed to be fine when he was with us and I wish him all the best."

Bierhoff was less impressed with Schalke general manager Andreas Muller, who accused the national team set-up of damaging his player mentally.

Muller claimed Kuranyi had never been given a fair chance with Germany and defended Kuranyi for walking out, even hinting that he did the right thing.

"I know he is only trying to protect his own player, but I don't really understand what Muller said," added Bierhoff.

"Surely it cannot be doubted that how Kevin reacted was wrong."