Neil Lennon will give Scott Brown until Saturday to prove his fitness for Celtic's clash with Dundee United.
The midfielder pulled up with a groin complaint during the warm-up prior to Scotland's Nations Cup win over Wales on Wednesday.
Scotland boss Craig Levein took the decision to withdraw the Celtic skipper, a decision Lennon called "sensible".
With a clash with Dundee United at Tannadice looming on Sunday, Lennon will give his player every chance to prove his fitness.
He said: "At the minute Brown is probably 50-50. We will have to wait to see how he is.
"I think he felt it previous to the international game and obviously he went out and warmed up and it felt stiff and sore.
"Scotland to be fair didn't want to take any chances with him, which was, from our point of view, the right decision.
"I don't have problem with him going with Scotland and it was a sensible decision.
"We have cover but we will see how he is tomorrow, another day might make a big difference. Obviously he is a very important player for us.
"Ideally you don't want to take risks and lose him for a longer period but we will make that decision tomorrow."