Celtic defender Daniel Majstorovic is expected to be sidelined following a suspected fractured cheekbone and eye socket.
The Swede was taken off in the first half of the Hoops' 2-0 win at St Johnstone after he clashed heads with David Robertson at McDiarmid Park.
Bhoys boss Neil Lennon disagreed with Saints manager Steve Lomas, who believed that Majstorovic's challenge was unnecessary.
"It was a perfectly good full-blooded challenge from a centre-half who only had eyes for the ball and he ended up worse off for his own bravery," said Lennon.
"There was nothing wrong with the challenge at all. It looks like a fractured cheekbone and it could be a fractured eye socket as well.
"It is a big blow because he has been immense for us. We will have to wait to see the extent of it but it looked a real sore one."
Celtic's win has kept them four points behind leaders Rangers in the SPL table.
