Madrid's top goalscorer Mbappe is not expected to feature at the Santiago Bernabeu against Pep Guardiola's side because of the knee problem which has bothered him since last December.
Carreras "has been diagnosed with a muscle injury in the calf of his right leg", Madrid said in a statement Monday, without specifying how long he is expected to miss.
Los Blancos have several absences ahead of the clash against Man City, with Jude Bellingham, Eder Militao, Rodrygo Goes, Dani Ceballos and David Alaba all recovering from injuries.
The biggest worry for Madrid is Mbappe's likely absence, without a clear timeline for when the France captain will be back in action, although Spanish media say he is targeting the return leg next week.
Mbappe has missed Madrid's last three matches and recently went to Paris for tests and treatment on his knee.