Neil Lennon will target a new centre-half in January after Christopher Jullien's injury setback.
The Frenchman is ruled out for up to four months after rupturing his knee ligaments in the 3-0 win over Dundee United on Wednesday night.
His absence proved to be costly at Ibrox as his replacement Nir Bitton was sent off in the 1-0 defeat to Rangers.
And the Northern Irishman revealed Celtic will be dipping into the transfer market for cover while Jullien is on the sidelines.
Lennon said: “It is an area where we will probably look to bring someone in.
“He is going to be out for a few months. He has ruptured ligaments in his knee. Obviously that was a blow coming in to the game but I thought we were good."
Celtic will travel to Dubai for a mini winter training camp this week with their next game against Hibs on January 11.
And Lennon says hopefully the players can press the reset button and have a strong second half of the season.
He added: "We lost this time last year, we went on a brilliant run. Wee bit of warm weather, get some R&R, refresh and we go again."
