Roland Lamah and Pablo Hernandez are in contention to start in the Midlands after recovering from hamstring strains, while Michel Vorm could be recalled in goal after missing six weeks because of knee surgery. Neil Taylor may get a run out in defence if first-choice left-back Ben Davies is rested.
A 2-1 victory over Manchester United in the third round was Swansea's only win in their last 10 matches in all competitions, but Lee Clark's Birmingham side have been in contrasting form.
Before falling to consecutive Championship losses, the Blues had gone 10 games without defeat and the likes of Andrew Shinnie and Wade Elliott could be recalled in midfield to help their team discover the winning touch.
Brian Howard, who joined on a free transfer from Bulgarian side Levski Sofia last week, is among the players who could make way while Colin Doyle may be restored in goal in place of Darren Randolph.