Rangers captain Lee Wallace out for two months with injury
The left-back faces up to two months out with a groin injury, manager Pedro Caixinha has confirmed.
But both Bruno Alves and Declan John could still face Celtic on Saturday after going off with injuries during Tuesday's Betfred Cup win over Partick Thistle.
Wallace had already been ruled out of Saturday's derby clash at Ibrox after going off in his team's previous trip to Maryhill, and a trip to a specialist in Manchester has revealed the extent of his lay-off.
Caixinha said: "He needs three weeks to rest totally and then after he needs three to five weeks to get totally recovered, so it's six to eight weeks in total."
Alves limped off with a thigh injury during Rangers' 3-1 extra-time victory while John, Wallace's replacement at left-back, went off nursing a thigh problem after shaking off an ankle knock to start.
Caixinha said: "After extra-time you need even longer to recover. So we are still assessing Declan, Bruno and all the others who finished the game."
Asked if he was confident John and Alves would play, Caixinha said: "I'm always positive, always confident but I need to assess. As soon as we have the information we will take a decision.
"I have a clear idea of what we want from Saturday's game. Of course the actors may be different and if the actors are different we may have to change a bit of the script - but not too much.