The captain hirpled off just after the hour mark in last night's 2-1 defeat to Benfica in Lisbon and is now likely to require surgery.
Neil Lennon's hope is that the midfielder will return for Celtic's European fixtures in February, Barcelona's defeat of Spartak Moscow having ensured that the club will play in continental competition after New Year. The imminent focus, though, is on ensuring those games will be in the Champions League after the defeat moved Benfica ahead of Celtic by virtue of their better head-to-head record.
"Scott has run his course; we may have to book him in for surgery," Lennon said. "We are looking at eight to 10 weeks. He has been pushing himself to the limit and we can't keep asking him to put himself through the amount of distress that obviously he was doing towards the end of his time on the pitch. I think it is time to get the problem addressed and hopefully he will have something to look forward to in the new year."
Lennon was alluding to the fact that Celtic will advance to the last 16 of the Champions League should they secure a better result against Spartak at Parkhead than Benfica can manage in Barcelona.
"I think Benfica are capable of getting a win in Barcelona, for they are an excellent side," Lennon cautioned. "But we have to make them do that. I don't know what mindset Spartak will be in; they might want to spoil our party.
"No-one gave us a prayer coming in to this competition but these players have been exceptional; they have made a name for themselves and we are still in with a good chance of qualifying."