Muller only arrived on Tuesday after playing for Bayern Munich in their Champions League final defeat by Inter Milan in Madrid on Saturday.
"Thomas Muller slipped and slightly scraped his knee and injured his chin that required some stitches," team spokesman Harald Stenger said. "But he did not sustain any bone or muscle injuries."
Germany have already seen first choice goalkeeper Rene Adler, captain Michael Ballack and midfielder Christian Traesch ruled out with injuries from the June 11-July 11 tournament in South Africa.
Germany have been drawn alongside Ghana, Serbia and Australia in the group stage.
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