Rangers striker Kenny Miller faces a "significant" stint out of action with a ruptured hamstring, adding to the club's already considerable injury woes.
The 37-year-old frontman tore his hamstring during last week's win over Hibernian at Easter Road.
Caretaker boss Graeme Murty expressed optimism in the days after his side's Leith triumph that Miller could feature against Celtic in the Old Firm match at Parkhead on December 30, b ut those hopes have now been snuffed out with confirmation the player requires a lengthy recovery period.
"Kenny's is going to be more significant than we thought," Murty told Rangers' website. "Unfortunately it looks as though he has a rupture of his hamstring, so he is going to have a significant amount of time out.
"We were hopeful given the way he presented, and given the fact his range was OK, but once we've scanned it, we have seen there is significant damage in there, so we have to be more conservative in our approach with him.
"That's a painful one for him and a sore one for the group as he is an integral part of everything that we do around the place. If anyone knows Kenny, they know the standards that he drives.
"So we are going to miss him."
It is more bad news for the Ibrox side, having learned last week that midfielder Graham Dorrans faces three months out after ankle surgery.
The Light Blues are also without midfielder Jordan Rossiter and back-up goalkeeper Jak Alnwick through knee and ankle injuries respectively, but Lee Wallace is making progress from the groin problem that has sidelined the skipper since September.
Murty added: "We are obviously going to miss Graham after his operation, while Jordan has had an injection which will hopefully lead him to go on further than he is currently.
"Jak Alnwick has also had an injection in his ankle as he has had a problem for a small amount of time. We are hoping this injection could clear it up, but we are going to have to give him a rest for a period, but hopefully that's not too long.
"Lee is getting closer, but I think he is going to need minutes. It's encouraging to see the signs and encouraging to see the speed and the tempo he has been able to play at.
"So having Lee back strengthens us not just in terms of numbers, but also in terms of the kind of character he is. He is the club captain, and having him involved is obviously something we want to get done as soon as he can."
Meanwhile, Murty has confirmed Carlos Pena and Fabio Cardoso will be available for Saturday's trip to Kilmarnock despite being left out of the squad for Saturday's home defeat to St Johnstone.