Manchester City boss Pep Guardiola has confirmed an injury for Kyle Walker.
The defender asked to be substituted with 10 minutes remaining for their 1-1 draw with Aston Villa and was replaced by the returning Nathan Ake.
However, the nature and severity of the issue aren't yet known, with Guardiola yet to speak to his medical staff.
"He had some problems in the first half and in the second and he could not continue," Guardiola said.
"We will see how he is. I didn't speak to the doctors."