City were left to rue a series of first-half chances not taken as Birmingham escaped Ashton Gate with a clean sheet despite being outplayed for long periods.
Blues have designs on finishing in the play-off places and did improve in the second period, but by that time they should really have been faced with a mountain to climb.
Tomasz Kuszczak was in fine form in the visiting goal, but City will feel they should have had more than a point to show for their efforts on a day when MK Dons did not play and Rotherham United were well beaten.
City’s interim management duo of John Pemberton and Wade Elliott handed debuts to two more new arrivals after Ben Gladwin and Alex Pearce featured at Leeds United last time out.
Now back on home territory, Gladwin and Pearce would have to settle for places on the bench as Lee Tomlin and Scott Golbourne were given starting berths – for Golbourne a second debut, having begun his career at Ashton Gate more than ten years ago.
Tomlin would start the game from the left flank with Luke Freeman on the right and Bobby Reid in a ‘number ten’ role behind Jonathan Kodjia, matching up with Birmingham’s 4-2-3-1 formation.
It was a formula that looked to be working right from the very first minute as City stormed out of the traps.
Marlon Pack connected sweetly with a difficult bouncing ball to force Kuszczak into a first notable save inside 30 seconds, before Tomlin showed his class to kill the ball in one touch and feed a low pass into the box left by Reid and fired wide by Kodjia.
Pack was involved again in less familiar fashion when he traded passes with the returning Mark Little and surged towards the byeline, before pulling a brilliant low ball across the box that unfortunately none of his team-mates anticipated.
The City midfielder was looking in the mood and soon met Freeman’s cushioned volley from the touchline with a dipping half-volley that Kuszczak needed two attempts to gather.
Birmingham had come into the game on the back of two impressive 3-0 wins against fellow promotion chasers Derby County and Ipswich Town, but seemingly had no answer to City’s high-tempo approach.
The home side’s obvious confidence was summed up by Reid’s ambitious volley from 30 yards that sailed wide, while the City fans roared their team on, suitably encouraged by the opening exchanges.
Top scorer Kodjia was leading the line and warmed the gloves of Kuszczak on 17 minutes. The obvious tactic from defender Michael Morrison was to stop the Frenchman turning inside as he raided down the left, so Kodjia went straight for goal in trying to catch out the former Manchester United keeper at his near post.
The only thing missing from a dominant display was a goal to show for it – not for the first time this season.
But it was not for the want of trying and City continued to press. Tomlin shaped a curling shot just beyond the far post before Freeman played a one-two with Reid and hit a low drive too close to Kuszczak from 20 yards.
Birmingham were always likely to come into the game and had their first glimpse of an opening shut down by Nathan Baker in typically uncompromising fashion.
Lured in by a heavy touch from Jon Toral, the Aston Villa loanee left nothing to chance and went straight through the midfielder to earn the first yellow card midway through the first half.
Toral had just managed to prod the ball through to Clayton Donaldson, who might have had the opportunity to score had he not been so quick to call for Baker to be punished.
Spanish midfielder Toral is Blues’ chief creator, but his afternoon would not last much longer as he hobbled off to be replaced by Jacques Maghoma before the interval.
But it was an isolated breather for the visiting backline, as Kodjia and Tomlin soon resumed their quest to make the breakthrough.
Kodjia should have done better from Reid’s left-wing cross with a header that did take a deflection on its way over, but never looked like a clean connection from only six yards out.
Tomlin then tried another curler looking for the bottom corner this time blocked, before a left-footed strike cannoned against a defender and threatened to wrong-foot Kuszczak who held his ground.
With four added minutes to prolong City’s dominance, there was still time for Tomlin to turn Paul Caddis inside and out, prompting the defender to leave a leg hanging and the attacker to go down.
But with the crowd expectant, Rob Lewis opted to book Tomlin for a dive, ensuring the half-time whistle that followed was initially greeted by jeers for the referee before City were applauded off.
There was no immediate change in the pattern of play after the restart. Tomlin showed a combination of close control and brute force to leave two defenders in his wake before looking the other way as he played the ball through for Kodjia.
This time Kuszczak was ironically beaten only for the offside flag to maintain the deadlock.
There was no doubt Gary Rowett would have delivered some strong words to his side at the break, and Birmingham did improve as the second half wore on.
City would have to survive a goalmouth scramble after Maghoma waited too long to shoot, before left-back Jonathan Grounds produced a cross that flashed across the six-yard box but just beyond the stretching Donaldson.
Rowett gave £1.5m signing Diego Fabbrini half an hour to impress, having snapped up the Italian midfielder from Watford in the week, prompting his side to enjoy much more possession.
Pemberton counteracted that by introducing Wes Burns for the tiring Tomlin to give the visitors something to think about on the break.
Kuszczak may have been busy at one end but Richard O’Donnell had been a virtual spectator at the other, making his flying save to keep out Maghoma on minutes all the more impressive.
The winger vacated his touchline to pick up possession and jinked his way across the edge of the box before shooting towards the top corner, forcing O’Donnell to stick out a left hand and make an excellent stop.
O’Donnell would need to make a more routine save from Donaldson down by his near post before Burns began to get increasingly involved.
The Welshman appeared to get there first before being upended by the last defender from one City attack, but Birmingham escaped as the ball ran through to Kuszczak, while Burns found a promising position on the right flank from a pass by Pack only to send his cross straight out of play.
Fellow replacements Aaron Wilbraham and Kieran Agard both had chances late on, notably an Agard header from a brilliant Freeman cross that just skimmed off his hairline, but the goal City’s attacking play merited would not come.