Alistair Johnston is set to miss three months after the hamstring injury he suffered against Kairat Almaty.
The full-back had to be taken off on a stretcher after pulling up in the first half of the Champions League contest at Celtic Park.
Johnston then used crutches as he returned to the bench to watch the remainder of the match.
Now, Brendan Rodgers has revealed Johnston will be sidelined for three months after a scan on the injury issue.
Quizzed on Johnston, the Celtic boss said: "Not great. He will probably be about 12 weeks.
"He had his scan yesterday, so it's disappointing for him because he's come back and started well.
"I think when you lose any player of that calibre, it is a disappointment, but it will provide an opportunity for someone to step in.
"We know we have Tony, I have got young Colby Donovan who is a young player here who has really impressed me over the time I've been back.
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"In this last 12 months he has made great strides.
"Of course, for Ali, we just want to make sure we are in a good position in all competitions when he gets back."
Rodgers is looking internally for a right-back replacement in the immediate aftermath of the Johnston injury rather than turning to the transfer market.
Meanwhile, Celtic will also be without Adam Idah and Auston Trusty for this weekend's match after the pair suffered injuries.
Idah is managing a knee problem with Trusty facing a spell out through an ongoing knock.
Rodgers confirmed: "Adam Idah is struggling with his knee.
"Auston Trusty could be out for a bit with the plantar fasciitis that he has had."
