Reading boss Brian McDermott admits they have no date on Alex McCarthy's return.
McCarthy suffered a labral tear during the 1-1 draw with QPR a month ago and after failing to respond to treatment, it was decided an operation was necessary.
The 23-year-old had been Reading's first choice goalkeeper since September, edging out Adam Federici in the position.
"We don't want to put a time frame on it except to say it will be a long time. A decent amount of time," said McDermott.