Rangers captain Steven Davis could miss the last five games of the season after being told he might need surgery on a groin injury.
Davis limped off early in the club's most recent game, a victory over St Mirren 10 days ago, and will miss Saturday's trip to face Hearts.
Manager Ally McCoist told the club's official website: "Davo is struggling a little bit. It's not been confirmed yet in terms of the extent of the injury, but it looks like he'll probably need a wee operation towards the end of the season.
"When he gets that done will be decided after a chat with the medical staff, but he won't be involved at the weekend, that's for sure. Missing our remaining games is a possibility and that's a concern, but he's going to see a specialist.''
McCoist, though, has some cause for optimism ahead of the remaining five Premier League matches.
"It's certainly calmed down a lot since he came off in the game against St Mirren,'' McCoist said. "It's still a niggle for him, but we'll know more once he's seen the specialist.''
Full-backs Steven Whittaker and Lee Wallace should return against Hearts after missing the Saints game through injury.
"Steven is already back training with the team and we're hopefully going to have Lee joining in on Wednesday or Thursday,'' McCoist said. "I would be very hopeful that both lads will be involved at the weekend.''
The loss of Davis could offer an opportunity for midfielder Rhys McCabe, who received a Scotland Under-21 call-up today after breaking into the first team last month.
McCoist said: "Rhys obviously played well in the Celtic game and we had him on again when Steven came off against St Mirren. We have one or two others who can play in that position, though.
"Maurice Edu has been doing all right and we have other options in there but Rhys would certainly come in to our thinking. He hasn't looked out of place at all, and he's a confident lad. He still has miles and miles to go, but he's had a few good games.''