Bayern could seek compensation as they believe it is an aggravation of the injury the 26-year-old suffered just prior to the World Cup finals, playing in a friendly for the Dutch against Hungary, but recovered sufficiently to play a decisive part in the Netherlands march to the final.
"This diagnosis came as a shock," said Robben, following the examination by team doctor Hans-Wilhelm Müller-Wohlfahrt after which an MRI revealed a hole of about five centimetres in the muscle.
"I felt in really good shape, I played in four matches at the World Cup and I never felt the slightest pain," he said.
Bayern president Karl-Heinz Rummenigge was seething at the news as he had criticised Robben's selection for the finals squad after he suffered his initial injury and claimed he had asked world governing body FIFA to act as a mediator in the dispute between the club and the Dutch federation.
"Yet again we have to pay for the folly of a national federation and for an incorrect diagnosis," he said. "We are extremely disappointed."
Robben, who inspired Bayern to the domestic double as well as the Champions League final last season, will miss the opening games of the Bundesliga as well as the first games in the Champions League group stage which gets underway in mid-September.
"It is a serious injury," commented Müller-Wohlfahrt. "I find it irresponsible that the Dutch did not diagnose the injury more precisely and they allowed him to play."
Robben, who is nicknamed the 'Crystal glass player' for his fragility, had an outstanding World Cup and had a golden chance to put the Dutch ahead in the final against Spain only for Iker Casillas to save - the Spanish went onto win 1-0.