Pedro Mendes has confessed he'll miss the Old Firm game at Celtic Park on January 3, reports the Scottish Sun. The Portugal star, missing for eight weeks with a knee injury, said: "That game may be too soon.

"I just take it day by day and keep building up the knee.

"Of course, there's also match fitness and I need a good week's training in the legs before that.

"It's difficult to put a definite date on when I'll be back because of any reaction you can get from the work you did the day before.

"But I definitely hope to be back before the end of January."

Mendes suffered posterior ligament damage when he was forced off at half-time in the humiliating 4-1 Champions League loss to Unirea Urziceni.

He added: "I felt a crack and some pain, but then the doc and physio examined me and I was okay. There was suddenly no pain.

"But after 15 minutes I started struggling a bit and for the last ten minutes of the first half I was in agony.

"It was an important game for the team though and you just didn't want to go off. But by half-time I just couldn't carry on.

"In the second half someone came in and said it was 2-1, then 3-1. It wasn't a good game."