Celtic defender Daniel Majstorovic has undergone surgery on the fractured cheekbone he sustained in the 2-0 win against St Johnstone on Sunday and will be out for six weeks.
Majstorovic had to go off in the first half at McDiarmid Park following a challenge on Saints midfielder David Robertson, who was also replaced soon after.
Majstorovic's operation was successful but it could be early February before he can return to training.
"Daniel Majstorovic underwent surgery yesterday, on the fractured cheekbone he suffered in the 2-0 win against St Johnstone on Sunday,'' a club statement read.
"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. Saturday's match, however, is likely to come too early for the trio.
Midfielder Kris Commons is set to resume training on Monday after overcoming a thigh strain. Defender Glenn Loovens, who tweaked his right hamstring against Hearts ten days ago, will also return to training later next week.
Manager Neil Lennon also heard good news regarding Mark Wilson's knee injury.
The defender has made good progressed 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.