Charlie Mulgrew will be monitored in the lead-up to Celtic's meeting with Hibernian on Saturday.
The star defender was subbed off at half-time of the 2-0 win at Dundee on Wednesday because of a rib problem and is in doubt for this weekend's trip to Easter Road.
"Charlie has damaged a rib or pulled a muscle in the rib area," said manager Neil Lennon.
"He was finding it hard to breathe so he will have to be assessed. He was playing very well and had a great first half. That was an enforced change."
Celtic went seven points clear on top of the Scottish Premier League table on Boxing Day and will look to extend that when they take on Hibs, quite possibly without Mulgrew in the side.
