Birmingham will be without key midfielder Guirane N'Daw after he was forced off in Easter Monday's thrilling 3-3 draw at West Ham nursing a hamstring strain, with scans yet to confirm how long he faces on the sidelines.
Jonathan Spector (thigh) is not quite ready and Stephen Carr (knee) is battling to play again before the end of the season, but fellow defender Pablo Ibanez is expected to be back in contention against the Robins after his hamstring injury.
Andros Townsend is likely to replace N'Daw in a reshuffled midfield although Chris Hughton could opt to recall Nikola Zigic in attack and drop Wade Elliott, who played behind Marlon King against the Hammers, back into midfield.
Bristol City will be without suspended striker Brett Pitman for the trip.
Pitman was dismissed for a foul on Coventry's Jordan Clarke during the Robins' crucial 3-1 victory over the Sky Blues on Easter Monday and serves the first game of a three-match ban.
Derek McInnes will be hoping his side move further clear of the relegation zone with a third consecutive victory, but they will have to do so without a number of first-teamers.
Lewin Nyatanga is struggling with an ankle problem and James Wilson has been ruled out for the season with his own ankle knock.
Midfielder Marvin Elliott (Achilles) and striker David Clarkson (ankle) will also remain sidelined for the remainder of the campaign.
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