Man City are hopeful Vincent Kompany has not suffered another injury setback after failing to finish Wednesday's game at Swansea.
The Belgium international was making his first appearance of the season in the EFL Cup tie at the Liberty Stadium having missed the last four months due to a thigh injury.
While the night overall went well for City as goals from Gael Clichy and Aleix Garcia secured them a 2-1 victory, the sight of Kompany walking down the tunnel in the final few minutes of the match left a sour taste in boss Pep Guardiola's mouth.
After making just a handful of appearances last season due to a string of injuries, Guardiola had been hopeful the club's medical staff had got to the bottom of the City skipper's issues.
The Spaniard is now keeping his fingers crossed Kompany's latest problem does not keep him out for long.
Guardiola said: "The doctors are speaking with him and seeing what's up.
"Hopefully, it will not be a big problem. We're going to wait for the results from the doctors.
"(His performance) was good. It's not easy after a long, long time without playing. Defensively, he was so strong - he played really good.
"Once they scored the goal, after I said: 'What happened?' They said that Vincent had gone to the locker room. Hopefully, it will not be a big problem. We will have to wait.
"If he's injured, he's injured. He cannot stay on the pitch."