Aleks Zinchenko appears to have undergone a procedure in Barcelona after missing the last Manchester City fixture with a knee injury.
Zinchenko was initially ruled out of the win at Crystal Palace with illness, according to City, before the club tweeted that he had suffered a knee injury to keep him out of the win against Atalanta in the Champions League.
City said: "Oleksandr Zinchenko has suffered a knee injury that means he misses tonight’s game at home to Atalanta.
"The Ukrainian will be assessed over the coming days to determine the extent of the problem.
"Everyone at City wishes Oleks a speedy recovery."
On Friday, Zinchenko then posted to Instagram from his hospital bed with the caption: "On the way back."
The post was tagged with the location as Barcelona, where City often use doctor Ramon Cugat to perform surgery on players with knee injuries.
City stars including Benjamin Mendy, Aymeric Laporte, Kevin de Bruyne and Ilkay Gundogan have all travelled to the Spanish city for recovery from injury.
If Zinchenko has undergone surgery, he would be expected to be out of action for some time, with Mendy, Laporte and De Bruyne all facing lengthy spells on the sidelines over the last year with knee injuries of their own.
