The newcomers to the top-flight this season have battled their way to a respectable 13th place but could suffer for their indiscipline during the second-half of the season.
Blues boss Steve Bruce believes referees need to be less forthcoming in brandishing cards and it is no surprise with his side suffering more than most.
Top offenders
Striker Geoff Horsfield's dismissal against Charlton saw him become the third St Andrews player to get his marching orders this season.
Bruce's players have been given 47 yellow cards on top of the sendings-off.
Fulham are second on the list of offenders with five red cards to their name but they do not have as many yellow cards as Birmingham.
Liverpool have the best disciplinary record and - along with Tottenham and Sunderland - they have not had a player sent off this term.
Meanwhile, Professional Footballers' Association deuty chief executive Mick McGuire says players are holding back from tackles for fear of punishment.
"Some players maybe feel they can't tackle," said McGuire.
"They are trying to win the ball fairly and get sent off.
"If it is a legitimate attempt to win the ball, one would say 'okay, if he keeps doing it, then you have to look at it.'
"But there are times during this season where players have been sent off for nothing much more than winning the ball."
He added: "The referees have a very difficult job and have improved their quality.
"Sometimes they might want to use their own discretion and can't.
"When they are advised that is a yellow card, that is a red card, it does not give the players much scope."