Manchester City boss Mark Hughes has conceded Martin Petrov faces up to four months on the sidelines after his knee injury failed to respond to treatment.
The Bulgarian has been out of action since sustaining the knee problem on international duty last month.
It was hoped the flying winger would not need to undergo surgery, but Hughes has admitted it looks increasingly likely that Petrov will be forced to go under the knife.
"Martin is going back to Spain to see his surgeon. The feeling is that the strengthening work we have been doing is not, unfortunately, going to be the answer," Hughes told the club's official website.
"He is going to go and see if there has been any progress, and whether we are to continue with what we have been doing. If the decision is that he needs an operation, then so be it.
"It won't end his season, but it will be a significant length of time that he will be out, three or four months most probably."
BoostThere was better injury news on Michael Johnson with the midfielder being given the green light to return to training.
The England Under 21 international has been out of action since September with a troublesome groin problem and Hughes is keen to have him back available again.
"Johnno trained on Monday and it did not look like there was a reaction. We'll look to get him out again to work through the injury, hopefully if we do that then he'll be playing again.
"His absence has been frustrating because thinking back to the Sunderland game he played really well there. 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."