Celtic boss Neil Lennon has confirmed defender Kelvin Wilson could be out for up to six weeks through injury.
The 26-year-old has started six of the Hoops' seven league games this season before picking up a problem in Wednesday night's Scottish League Cup win at Ross County.
Wilson was set for a scan on Friday but is definitely out of Saturday's league game at home to Inverness.
"We don't know how long he is going to be out for until we get the results of the scan but it looks like he has a slight tear in the Achilles," said Lennon.
"It depends on the significance of the tear, we are hoping that it will be, at best, two to three weeks.
"It could be four to six weeks but we won't know the extent of it until the scan comes through."
Fellow defenders Cha Du-ri (hamstring) and Emilio Izaguirre (broken ankle) are already out, while skipper Scott Brown (ankle) has been ruled out of the Inverness game and has only a small chance of playing against Udinese in the Europa League on Thursday.
With midfielder Kris Commons out with a groin injury and Charlie Mulgrew suspended after being sent off in last week's Old Firm defeat, the Hoops squad is still stretched despite Georgios Samaras (ribs), Mark Wilson (knee) and Paddy McCourt (calf) recovering from their respective injuries.
"Of course, Charlie is suspended," Lennon added. "He has been playing very well and losing him is a blow.
"We will have to manoeuvre the back four, which isn't ideal but we have good, experienced players in those positions and I expect them to deal with it tomorrow."
But Lennon has admitted he is keeping an eye on Dundee United youngster Scott Allan.
Tannadice boss Peter Houston revealed his disappointment that the 19-year-old midfielder, who is out of contract at the end of the season, had rejected "the best deal this club has ever offered to a teenager".
And asked if Allan was on his radar, Lennon said: "Probably, yes.
"He is a young, good player who has performed very well at SPL level and he has come to my attention through our scouting system."