Bayern Munich have confirmed that Manuel Neuer has suffered a foot injury which will require further medical tests.
The World Cup-winning goalkeeper picked up the knock during training on Monday.
Early reports suggest that the 31-year-old has damaged a bone in the same foot that he broke last season.
@Manuel_Neuer suffered a foot injury during training today and will not travel to Schalke. He will undergo further examination tomorrow. pic.twitter.com/cqp8szio3l — FC Bayern English (@FCBayernEN) September 18, 2017
Neuer endured a hairline fracture to a metatarsal in his left foot back in March, during which time he had the bone pinned and returned to action shortly afterwards.
The problem was, however, to be exacerbated as he sought to play on and he was eventually forced to concede defeat following a Champions League quarter-final reversal against Real Madrid.
Neuer ended up spending 133 days on the sidelines, before coming back into the Bayern fold in August.
He has remained a key figure for the Bavarian giants at the start of their Bundesliga title defence, but is now facing another spell on the sidelines.
Having been forced out of training, Neuer has already been ruled out of a meeting with Schalke on Tuesday.
Bayern have also announced that he will undergo further examinations before a full assessment of his injury is delivered.