Carlisle United will be without defender Stephen O'Halloran for up to eight weeks with a cartilage injury in his knee that requires surgery.
O'Halloran, 23, has been plagued by injuries throughout his career, twice rupturing his cruciate ligament and he slipped a disc while at Coventry.
The Republic of Ireland international has made five appearances since his July move to Brunton Park.
His last outing came in September's 2-1 home defeat by Hartlepool United.
Meanwhile, defender Steven Swinglehurst is also out with a cartilage injury in his knee.
The 19-year-old, on loan at Kendal Town, will also undergo surgery and faces up to nine weeks on the sidelines.