New loan signing 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.
The Northern Ireland international was in the right place to fire Blues in front early on but Connor Goldson’s header put the high-flying Seagulls back on level terms before the break.
And centre-back Lewis Dunk’s bullet header early in the second-half decided the contest.
Gary Rowett rung the changes with recalls for Jonathan Spector, Maikel Kieftenbeld, Jacques Maghoma and Clayton Donaldson.
There was a surprise fifth difference to the side that lost at Charlton at the weekend with Lafferty unexpectedly passed fit to start.
The forward borrowed from Norwich City was into the action early on, trying his luck with a fierce 25-yard drive that was bravely blocked by Dunk.
Blues had an almighty scare on 10 minutes when Bruno’s back-post header created panic inside the hosts’ six-yard box.
The ball was twice scrambled off the goal-line before Beram Kayal’s shot was blocked by his own man and finally Jiri Skalak crashed a low effort into the sidenetting.
But after surviving that hairy moment, it was Blues that edged in front on 16 minutes with Lafferty marking his debut with a goal.
Jon Toral’s delightful through ball created a shooting chance for Maghoma on the right side of the area.
The Congolese international side-footed a shot with his right boot across goal but it lacked any great power.
However, David Stockdale made a right mess of it, the visiting keeper dropping the ball invitingly in front of the alert Lafferty and the new Blues loanee gratefully poked it into the back of the net from 10 yards.
Blues’ tails were up and the home side were soon on the attack again, Donaldson charging forward from just inside the centre circle, but with Lafferty and Maghoma in support he opted to shoot from 25 yards and his effort flew well over.
Rowett’s men continued to push their opponents back and from another spell of pressure had a great chance to extend their advantage.
Maghoma got to the byline and his deflected cross looped up in front of an unmarked Toral but from 10 yards the Spaniard volleyed wide.
Blues were left to rue that missed chance as the Seagulls restored parity against the run of play on 29 minutes.
Skalak’s free-kick from wide on the left was met by Goldson’s flicked header, the ball drifting just inside Tomasz Kuszczak’s left post with the former Brighton custodian’s despairing hand unable to stop it from nestling into the bottom corner.
The goal lifted Chris Hughton’s men and it was their turn to enjoy a purple patch, with plenty of possession but Blues’ backline stood firm.
The closest the visitors’ came to another goal before the break was Goldson’s far-post header that flew just over the crossbar.
Brighton carried on where they left off after the interval and went in front within three minutes of the restart.
Kieftenbeld’s wayward pass gave the visitors a cheap corner and they took full advantage, Dunk rising highest to hammer an unstoppable header past Kuszczak from Skalak’s cross.
Only the fingertips of Kuszczak then stopped Brighton from extending their lead, the Pole at full stretch to turn Tomer Hemed’s audacious overhead kick around the post.
Blues finally responded just before the hour mark, Maghoma and Paul Caddis combining well wide on the right to launch a promising attack which ended with Kieftenbeld’s speculative 25-yard volley that was always veering away from goal.
There were then chances at either end with Skalak’s volley flashing across the Blues goal-line and away from danger, and Toral’s right-wing cross putting Stockdale into some difficulty as he flapped at the ball but Maghoma wasn’t close enough to take advantage.
Kazenga Lua Lua crashed in a shot from an almost impossible angle wide on the left and the ball fizzed only narrowly over Kuszczak’s bar as Brighton looked to put the game to bed.
Toral was presented with another good chance for Blues on 69 minutes. Caddis’ cross was deflected away from goal by Kayal into the path of the top scorer but he was again off target with his shot.
Blues made three late changes as Rowett looked to shake things up, David Davis, Diego Fabbrini and David Cotteril replacing Lafferty, Maghoma and Toral.
But try as they might, Blues could not find a way through a solid Brighton backline.
It was the visitors that almost added another goal to the scoreline, Spector doing well to stop Jamie Murphy’s shot from finding the net after a determined run from the Seagulls substitute.
And in the final minute of stoppage-time when, with Kuszczak up for a corner, James Wilson broke away but Caddis was able to get back and block the shot and prevent the ball from rolling into an empty net.
Blues’ hopes of making a late dash into the play-off picture are, in all honesty, looking more and more like a distant dream, now sitting 11 points adrift of the top six.
But until it’s mathematically impossible the fight will go on in what has still been a tremendous season for Rowett’s men.