"He is going to have an operation in America," said Kevin Keegan. "We've said it could be eight weeks out, but it could be as much as 10."
"It's a cartilage problem in his left knee. You can't help but feel sorry for the lad because he has had no luck with injuries whatsoever.
"But he is a good professional and we are hoping he will get over this in time to still play a big part in the latter part of the season."
After the sale of Darren Huckerby to Norwich for £750,000, City now have just three senior strikers - yesterday's scorers and Jon Macken - so Keegan may have to bring in back-up in the New Year.
"We possibly need to loan a forward if we can't buy one," he said. "The only one we want to get in is a striker of quality.
"But it is hard to know at the moment and I will have to discuss with the board what money is available so I can't say anything more at the moment."