Argentina's Nicolas Burdisso (C) and Germany's goalkeeper Rene Adler (R) fight for the ball during their friendly soccer match in Munich March 3, 2010.[Xinhua/Reuters Photo]

German No. 1 goalkeeper Rene Adler admitted on Tuesday he can not attend the World Cup in South Africa as rib injury.

"This was most difficult decision of my life," said Adler, a 25 year-old goalkeeper from Bayer Leverkusen.

"The pain is so great that I would not have been able to perform at my best over the longer term both in training and during matches," he said.

"In such a long and intensive tournament, that is unacceptable. You need players who are totally fit."

Rib injury has made Adler miss several matches and he returned on last Saturday for Bayer Leverkusen against Hertha Berlin

But an examination by Germany team doctor Hans-Wilhelm Muller-Wohlfahrt showed his injury is worse than first thought and he needs an operation to repair the ribs.

Germany coach Joachim Loew was very sorroy about Adler, but he said, Adler has to do that.

Loew said, he will discuss with the coaching team to decide who will replace Adler and announce the names for German team to South Africa in Stuttgart on Thursday.

Similar as Adler, midfielder Simon Rolfes, who will also be ruled out from German team this time, as he made a knee operation in January.