The 28-year-old picked up a knock to his right shoulder during Saturday's 2-0 DFB-Pokal final win over Borussia Dortmund, although it was initially thought to be a minor problem.
However, the former Schalke man was pictured Monday leaving a doctor's office following a checkup with his arm in a sling, prompting concerns that the injury could be more severe, with some reports suggesting he has suffered a broken acromioclavicular joint.
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And Bayern has since confirmed it will make an announcement on the precise details of Neuer's injury later Monday as concerns mount over whether he will be fit to take part in the World Cup, which begins next month.
The Bundesliga champion is also set to provide an update on the foot injury suffered by captain Philipp Lahm that forced him to be susbtituted during the DFB-Pokal final in Berlin, although Germany boss Joachim Low has already revealed he is "100 percent sure" the player will be fit for Brazil after speaking with him Saturday.