Celtic have confirmed Daniel Majstorovic will be out for six weeks after undergoing surgery on the fractured cheekbone suffered against St Johnstone.
The Swedish defender sustained the injury in Sunday's 2-0 win at McDiarmid Park following a challenge with Saints midfielder David Robertson.
He will now miss the upcoming Old Firm derby and it is likely to be early February before Majstorovic is ready to return to Neil Lennon's plans.
"Daniel Majstorovic underwent surgery yesterday, on the fractured cheekbone he suffered in the 2-0 win against St Johnstone on Sunday," read a club statement.
"The operation went well, but he now faces six weeks on the sidelines before he can return to training."
Meanwhile, midfielder Joe Ledley has returned to training after recovering from an ankle injury and will be available for selection this weekend for the home game against Kilmarnock.
Striker Anthony Stokes and midfielder Paddy McCourt, who both picked up slight calf strains, along with defender Adam Matthews, who suffered a twisted ankle, will return to training later this week, but are unlikely to face Killie.
Midfielder Kris Commons is set to resume training on Monday after overcoming a thigh strain, while defender Glenn Loovens, who tweaked his right hamstring against Hearts 10 days ago, will also return to training later next week.
Manager Neil Lennon also heard good news regarding Mark Wilson's knee injury, who has been making progress since undergoing surgery earlier in the season.
Medical staff have been impressed by his recovery and he will return to training in the first week of January.