Odsonne Edouard has made his return to Celtic after isolating in France, but remains a doubt for Saturday's clash against Rangers.
The striker tested positive for coronavirus on international duty with the U21s squad and was forced to quarantine for ten days.
Edouard arrived back in Scotland on Friday, but Neil Lennon says he still needs to be assessed ahead of Saturday's showdown.
He said: "Edouard is back today. He will be assessed - we are going through that procedure at the minute, so we will know more later on this afternoon.
"He has been a bit tired and isolated but we will go through the tests and we will see how he is."
Meanwhile, Albian Ajeti has provided Celtic with a timely boost as the striker returns from a hamstring injury.
Nir Bitton and Hatem Abd Elhamed are ruled out after they tested positive for the virus, but Celtic are pushing for Ryan Christie to be made available.
The midfielder was sent home by Scotland, along with Kieran Tierney, to isolate for 14 days after Stuart Armstrong came down with covid-19.
But the Arsenal star is set to be given the all clear to make his return against Manchester City on Saturday with his quarantine cut short.
And Lennon has demanded an explanation into why Christie should suffer a different fate.
He added: "We would be very confused and want answers, that Kieran Tierney is allowed to play and Ryan has been refused to play.
"It would be very confusing and I think our supporters would want to know the answers as well.
"Peter (Lawwell) and the board have been pushing this since day one and we have had no clarification, if anything we have just been met with complete resistance so far."
