City skipper Vincent Kompany is receiving treatment for a groin injury sustained in Wednesday's EFL Cup win over Swansea.
The Belgian centre-back was making his first start since May 4, but left the Liberty Stadium pitch moments before full time with the problem.
No date has yet been set for his return.
The positive for Kompany and City is that the injury is not a recurrence of the calf problems that disrupted his progress last season.
The 30-year-old looked in fine form against the Swans in midweek, defending with purpose and passing through the lines with precision.
Along with inform duo John Stones and Nicolas Otamendi, plus Aleks Kolarov's impressive outings at centre-back this season, a returning Kompany would give boss Pep Guardiola a tough selection headache.
We will bring you news of any update to Kompany's fitness as soon as we get it.