The Netherlands international has been out of action since damaging knee ligaments in the 4-0 setback at Wolfsburg in August.
Huntelaar had returned to training but suffered a further setback in training on Monday, with the club releasing a statement saying the 30-year-old could require an operation to resolve the issue.
"It doesn't really matter what the decision is on Klaas Jan Huntelaar," he said.
"He can't play until Christmas. It doesn't matter if he decides to have an operation.
"He might recover without one. Both outcomes are possible. The decision has not been made yet.
"We didn't rush him back before he got injured. Usually an injury like his is fine after eight weeks. He felt good.
"He took part in everything and this setback was an accident. He collided with someone in a bad position. This would still have happened even if it was two weeks later."
He added: "Timo Hildebrand is doubtful, he is suffering from back pain. Jones is questionable.
"We will also have to see about Boateng. The healing process is going well, but we have to wait to see if he is ready for Braunschweig yet. We will wait to make the decision."
