Gary Rowett lamented a miserable afternoon for striker Wes Thomas after a goalless draw against Cardiff saw him denied a second win in three unbeaten games as Birmingham's new manager.
Substitute Thomas had a close-range goal disallowed for offside before compounding his own misery with a silly 90th-minute red card for raising his hand to defender Sean Morrison.
The visitors, without a Sky Bet Championship away win all season, edged the first half but were pegged back in the second as Birmingham tried unsuccessfully to follow Tuesday's win over Watford with another home victory.
Rowett, who recently replaced Lee Clark, said: "I'm disappointed with the sending off. I haven't seen the incident again so I'll have to watch it before I make any judgement.
"Wes' reaction suggested he was a bit disappointed to have let one or two people down with what happened.
"There was no real need for him to raise his hand and it meant four or five minutes of hanging on rather than trying to get the winner."
Rowett was much more frustrated with the earlier disallowed goal.
"I'm not disappointed with the performance," he said. "It's a point and a step in the right direction as we look to build on the games we've had so far.
"I think for our goal, Wes was level. He was not offside at all. It was a very easy one to give, at the back post. It should have been a goal and then the game would have been different.
"They got it wrong. It was quite clearly onside."
Goalkeeper Darren Randolph was arguably Birmingham's man of the match as he impressively denied Cardiff three times in the first period, producing saves from Federico Macheda, Adam Le Fondre and a deflection off his team-mate Paul Robinson.
Macheda saw the flag raised as he fired in after a scramble in the box early in the second half, but Rowett's introduction of Thomas and Demarai Gray from the bench turned the game in Birmingham's favour.
Livewire Gray caused the visitors headaches and he had two or three half-chances, before whipping in a cross from the right in the 64th minute which Thomas smashed home only to be denied by the assistant referee.
Cardiff boss Russell Slade disagreed with his opposite number's assessment of that offside decision, but conceded his own side's disallowed goal was the right decision.
"I think we should have drawn first blood in the match," he said.
"We had two one-on-ones in the first half and should have taken one.
"In the second half it was a bit end-to-end with two offside goals which were actually offside.
"It's a clean sheet away from home though and that's important. It shows definite progress."
Slade dismissed any suggestion Morrison may have exaggerated Thomas' infringement by revealing the defender has a sore eye.
"It's swollen up and he's struggling to see," he said. "It's probably a bit bloodshot so he clearly caught him. He's a big lump of a centre-half but he needed treatment."