Northern Ireland international Kyle Lafferty introduced himself to the St. Andrew’s faithful in great style with a goal but it wasn’t enough to get anything from promotion-chasing Brighton.
Norwich loanee Lafferty, who shrugged off a groin injury to make his Birmingham bow, tapped in after 16 minutes when David Stockdale failed to hold Jacques Maghoma’s strike.
But two headers from Connor Goldson and Lewis Dunk condemned the hosts to a 2-1 defeat that left them 11 points from the top six after just two wins in their last 11 league games.
Boss Gary Rowett said: “I’ve warned the players if they think they can take their foot off the gas then they’ll be coming in on Sundays and their days off.
“I think I’d look a bit stupid if I said we could still get into the play-offs now, the gap’s 11 points. The goal just after half-time sucked the life out of us. It was all huff and puff after that.
“I was really pleased with Kyle, when I took him off a fan was screaming he was our only chance of a goal, but he hasn’t played a lot of football and needs to be fitter.”