Birmingham will be without Keith Fahey and Chris Burke for the visit of Millwall while Jonathan Spector will be assessed.
Midfielder Fahey returned from a lengthy absence due to compassionate leave to put in positive displays at Middlesbrough and Crystal Palace, where he was duly forced off with a troublesome hip injury and missed Monday's 3-2 home defeat to Wolves.
The Irishman is now likely to be on the sidelines the remainder of the season as Blues look to get to the bottom of the problem.
Winger Burke has missed the last two games due to ankle problem sustained in training and will again sit out, but fellow midfielder Spector could return from an ankle injury of his own and faces a race against time to feature against the Lions.
Marlon King, Stephen Carr, David Murphy and Will Packwood all remain unavailable due to injury as 11th-placed Blues aim to stretch the five-point gap that currently exists to the bottom three.
Millwall have no new injury concerns ahead of the trip.
But boss Kenny Jackett is still set to be without defenders Karleigh Osborne and Paul Robinson, along with wingers James Henry and Chris Taylor.
Osborne has a hamstring strain, skipper Robinson remains a long-term absentee with a groin problem and Henry is recovering from a knee injury.
Taylor is the closest to returning but remains a doubt due to a groin injury.
Defender Sean St Ledger came on for his debut in Monday's goalless draw with Ipswich following his loan switch from Leicester and should be involved again.
Jackett may shake up his attack after they drew another blank, with on-loan QPR striker Rob Hulse pushing for a start.