Dundee United defender Garry Kenneth will be out for three weeks after suffering a knee injury in the 2-1 defeat at Hearts.
Kenneth was forced off towards the end of the first half at Tynecastle on Saturday and will now miss a busy period for the Terrors.
Peter Houston's side face a fixture backlog in the SPL and Kenneth could miss the club's next six matches due to the injury.
"Garry will be out for three weeks after straining his medial ligaments," confirmed Houston.
"We are down to the bare bones and we have no centre-halves now."
The Scottish Cup quarter-final tie against Motherwell on 13th March or the SPL home date with Hearts three days later are likely comeback targets for Kenneth.