Rangers full-back Steven Whittaker has had a hernia operation and will be out for at least six weeks.
He has not played since Christmas Eve, but the club hope he will return in time for the home clash with Hearts on 3 March.
The 27-year-old is almost certain to miss Scotland's friendly with Slovenia on 29 February.
Kirk Broadfoot is a possible replacement, although he has been struggling with a knee problem.
The former St Mirren defender is set to have a scan on Tuesday evening, having missed Rangers's recent wins over Motherwell and Arbroath.
On-loan Arsenal man Kyle Bartley filled in at right-back for the Scottish Cup victory at Gayfield, only to be replaced by Jordan McMillan after picking up a knock.