Sebastien Bassong said he was disappointed not to leave St Andrew's with maximum points after Saturday's 1-1 draw.
The defender was back in the starting line-up for injured Younes Kaboul against Birmingham and marked his return by smashing home the opening goal after 18 minutes.
We dominated the first half against a team that has now lost just one of its last 27 matches at home in all competitions.
However, the key second goal proved elusive and the Blues gradually pushed us back in the second half, eventually equalising through Craig Gardner's header with 10 minutes remaining.
"We're really disappointed about the result," said Seb, who impressed in central defence alongside William Gallas.
"We expected to win after the first half. The second half was harder, we were sitting back and they were hitting the ball into the box.
"We had to deal with it, but it was difficult.
"We missed chances in the first half and we should really have killed the game and if you don't score those chances, you might concede and that's what happened. That was disappointing."