Bayern Munich and Germany goalkeeper Manuel Neuer will be out until January after surgery on his broken left foot.
The 31-year-old World Cup winner sustained the same injury to the same foot in April and suffered a repeat in training on Monday.
Bayern are in the same Champions League group as Celtic and Neuer will miss their remaining five games.
“The operation went perfectly, which is the most important thing for now,” said Bayern chairman Karl-Heinz Rummenigge.
“We are now looking to the future. Manuel will be back to his previous best and available in January.”