City fear top defender Danny Hone could be out for up to nine weeks after limping off in Saturday's 2-2 League Two draw with Rochdale.
He is due to have a scan imminently, but early signs are that he could be out for some time..
Jacko spoke to local radio and commented "Indications from the physio are that it's knee ligaments, which is six to eight weeks.
"That's what we fear but we don't really know until it's properly looked at and X-rayed."
Lincoln are short of defensive cover after the poor outings from Frank Sinclair, meaning that Lee Beevers may have to fill in at centre back and Aaron Brown will revert to an unfavoured left side slot.
The Imps may turn to trialist Moses Swaibu who is on an extended trial at Sincil Bank.