David Moyes says he will monitor Leighton Baines ahead of Saturday's home game against Swansea.
Baines started the 5-1 FA Cup third round win over Cheltenham on Monday night despite carrying an injury.
Moyes said: "Leighton's got a bad ankle problem which I need to watch and be careful with.
"I felt we needed him against Cheltenham because we had to respect the players at this level."
The England international netted the Blues' second goal against the Robins before being replaced after the interval by Magaye Gueye.