Smicer, speaking to the club's official website, said: "I had a problem at the end of last season with my right knee but because we had the European Championships I was able to play in Euro 2004 and it was okay but I came back for pre-season and knew it would be hard work. The knee is still sore and it was getting worse and worse.
"I had a scan and it showed that maybe I need an operation. If I need an operation then I will get that done on Friday.
"It is bad timing with the new manager just arrived. I didn't want to have an operation before the start of the season but if I'm not going to be fit for the start then there's not much I can do about it. If it's necessary to have it done now I'll have to have it done.
"If it's only a minor operation then I will be out for six to eight weeks but if it's the cartilage it will be longer."