Celtic are hoping Scott Brown and Anthony Stokes will be fit for the Old Firm derby after being ruled out of the Europa League tie against Atletico Madrid.
Brown is still struggling with an ankle injury which forced him to miss Saturday's game against Motherwell, while Anthony Stokes suffered a thigh injury in training.
Both players have not travelled to Spain for Thursday's game against Atletico, but assistant manager Johan Mjallby is keeping his fingers crossed the duo will be available for Sunday's clash at Rangers.
Mjallby, speaking at Glasgow airport before Celtic flew to Madrid, said: "I think it is too early to say.
"Unfortunately they will not be available for tomorrow night but they still have a chance for Sunday.
"Anthony has a thigh strain, he shouldn't be too bad but we were surprised to see that he picked it up in training yesterday and that's it, we have to deal with it."
Controversy continues to surround the tie against Atletico after Uefa confirmed they had rejected Sion's appeal against their expulsion from the competition, allowing Celtic to take their place in the group which also includes Udinese and Rennes.
Sion vowed to fight their expulsion but lost their appeal following a hearing on Tuesday, although earlier in the day, a Swiss regional court backed their fight to be reinstated.
Sion can take their case to the Court of Arbitration for Sport within 10 days of written receipt of the decision.
However, Mjallby said: "The main thing is that we are in the draw and that's the way it should be because they played with some players who weren't allowed to play and Uefa have made the decision that we are in the group stages."
Sion president Christian Constantin claimed his side also plan to travel to the Spanish capital but the former Celtic defender joked: "I don't care, good for them. If they can pay for the tickets and go and watch the game then fine for him.
"The most important thing is we are in the competition and we have been planning for it since we were told we are back in."