Rangers' Filip Helander could be sidelined until after the January winter break with what manager Steven Gerrard says is "quite a rare" injury.
The Sweden centre-back has not featured since limping off against Celtic in the League Cup final on 8 December.
He faces another month before being allowed to remove a protective boot.
"The doctor told me that, in his 25-year experience in medicine, he had only seen this issue on a couple of occasions," Gerrard said.
After an initial difficult start to his Ibrox career following his summer transfer from Bologna, the 26-year-old had become a regular starter in Gerrard's side and has now made 18 appearances for the team sitting second the Scottish Premiership.
"Filip won't be seen again until after the winter break," Gerrard said. "It's a foot issue. I'm not a doctor, but I'm told it's a unique injury.
"I think he's been in the boot for a couple of weeks now, so he will be in a boot until after Christmas and then it will be a case of building the fitness back up and whether there is a reaction from the injury because it's quite a rare one."
Rangers will also be without the suspended Alfredo Morelos for Friday's trip to face Hibernian after their top scorer was shown a second yellow card for aiming an inflammatory gesture at the Motherwell support in Sunday's 2-0 win at Fir Park.
"Alfredo has been different," Gerrard revealed. "You can see in his face he's disappointed not to be available. He's not a man who hides that disappointment very well.
"I think Alfredo has apologised to his team-mates after the Motherwell situation, but that's not important now. We have to focus on what's available to us."
Jermain Defoe, who scored a hat-trick in Rangers' 6-1 win over Hibs earlier in the season, will lead the line at Easter Road.
"We believe we have got the squad capable of coping without any individual," Gerard added. "Jermain's name in the game speaks for itself. We'll pick a team that's capable of getting the result we want from Hibs if they perform to their best."