Manchester City winger Martin Petrov will be out for up to four months because of a knee ligament problem.
Petrov, 29, was injured playing for Bulgaria in October and the problem did not respond to treatment.
"Martin is going to see a surgeon and he will probably stay and have an operation," said City boss Mark Hughes.
"If that is the case he will probably be out for three to four months. That would be a blow for us as he gives us more options."
Hughes added: "Unfortunately it is a frustration for us as it happened on international duty. That makes it a bit more difficult to take.
"Martin had a good pre-season and last year he was one of our outstanding performers. But at the moment it looks as though he will have to go in for an operation."
Petrov, who had only just returned from a hamstring injury, has a tear in his meniscus but he has not damaged the more serious anterior cruciate ligament.
Hughes has, however, received a boost after Michael Johnson returned to training following a groin injury that has kept him out since September.
"Johnno trained on Monday and it did not look like there was a reaction," said Hughes.
"We'll look to get him out again to work through the injury, hopefully if we do that then he'll be playing again.
606: DEBATE"His absence has been frustrating. He's a different type of player to the ones I have had available recently, but he's not been an option so it would be good to get him back."
~RS~q~RS~~RS~z~RS~29~RS~)