The 29-year-old midfielder was taken off before half-time during Celtic’s 3-1 defeat to RB Leipzig on Wednesday night due to a knee injury.
McGregor looked in discomfort and Celtic boss Ange Postecoglou took no chance of further aggravating the problem by taking him off.
The Celtic captain is due for a scan on Thursday to determine the extent of his injury and further diagnosis.
The Bhoys are hoping for the best but it has been claimed that they are not expecting the greatest of news.
Celtic are wary that the results of the scans will not be good and the midfielder could be facing a lengthy layoff.
McGregor has been ever present in the Celtic team for several years and was entrusted with the captaincy once club legend Scott Brown departed Parkhead.
Postecoglou has already been forced to deal with injuries to several stars this season and is not keen to lose his captain for a considerable amount of time as well.
