The Welsh international woke up at the team's hotel on Saturday morning with a fever and was sent home by the City management.
Speaking to the CT, Chris Coleman said: "Freddie woke up with a fever, so we packed him off home.
"I hope it is nothing too serious but he was sweating badly and didn't look at all well.
Eastwood missed Saturday's win at Barnsley and is currently doubtful for tomorrow night's trip to Doncaster Rovers.