City were beaten at home in the league for the first time since November as Sheffield United overturned a half-time deficit to avenge their opening day defeat at Bramall Lane.
A dour first half was lit up by Matt Smith’s 13th goal in his last 13 games shortly before the interval, but City were unable to kick on.
Instead Matt Done converted a scrappy equaliser ten minutes after the break and doubled his tally 13 minutes from time to turn the game on its head.
Jamie Murphy made sure all three points would be heading north to the Steel City with the Blades’ third goal, with City horribly exposed on the break trying in vain to chase an equaliser.
Steve Cotterill made one change to his side victorious over Port Vale in midweek, recalling Mark Little in the right wing-back role at the expense of James Tavernier.
The two teams had played a combined 81 matches in all competitions before the start of play, and there was no great urgency about either side in the opening minutes.
It was as if City and the Blades had agreed to give each other a breather in the middle of a gruelling schedule, which has left both teams with games in hands on their promotion rivals.
What played out was arguably the least memorable 45 minutes of football at Ashton Gate this season.
Jay Emmanuel-Thomas was the catalyst for City to click into gear against Vale, but never looked like producing a repeat four days later.
An ambitious chip from 30 yards left Iain Turner in the United goal untroubled, while a slick turn to leave him running at the back four was halted by referee Graham Salisbury, who called the play back to book Chris Basham for a foul on Joe Bryan.
By now the visitors had already lost the services of their most creative player, with Jose Baxter limping off after 24 minutes with what looked like a leg muscle injury.
But City would find a way to edge their noses in front four minutes before the interval via a familiar source.
Again it was an attack started by Bryan, who again took a late hit off the ball as he offloaded a pass out to Luke Freeman on the left touchline.
This time Salisbury allowed play to continue, and Freeman carried the ball into a crossing position before his deflected delivery dropped perfectly for Smith to steal in and score.
The striker read the flight of the ball quickest and prodded over the line from six yards with Turner stranded by the looping ricochet.
City started the second half brightly enough, with Emmanuel-Thomas and Freeman both firing low shots wide from distance before United scrambled home an untidy equaliser on 55 minutes.
It was a moment that made Cotterill see red. Little had been clearly fouled in a previous attack without being awarded a free kick, and when blocked off by Bob Harris, man in the middle Salisbury came to the same conclusion.
Already irate, the mood of the City boss was not helped when the Blades counter-attacked to score.
Adventurous right-back John Brayford produced a low cross that found its way through to Jason Holt, whose initial strike was parried by Frank Fielding before Done forced the ball over the line from point-blank range.
It was a real kick in the teeth for City, hardly troubled by the Capital One Cup semi-finalists up to that point.
But the response was good, as if Cotterill’s sense of injustice had rubbed off on to his players.
Bryan set about restoring the lead with a surging run into the penalty area, standing the ball up from the byeline for Emmanuel-Thomas to meet at the back post.
Just as the striker looked set to score from unusually close range, Harris was perfectly placed on the post to make a goal-line clearance and preserve parity.
With title rivals Swindon Town and MK Dons both behind, Cotterill smelled an opportunity to open up a seven point lead at the top and introduced Kieran Agard from the bench as an extra forward player at the expense of Wade Elliott.
But soon enough United had turned the game on its head. Murphy played a neat one-two to tiptoe into the box and square the ball for Done to score his second from a combined distance of less than six yards.
City were rocking, and within five minutes their visitors had wrapped up the points with a breakaway third.
Luke Ayling was dispossessed on the halfway line, leaving Murphy with a clean run on goal, eventually checking inside the covering Aden Flint and dispatching the ball in clinical fashion beyond the helplessly exposed Fielding.
City had gambled on turning one point into three, but the lead at the top remains unchanged with one more date ticked off the fixture calendar.