SHEFFIELD UNITED were on the receiving end of an Andreas Weimann hat-trick as Chris Wilder's side suffered their first defeat in 11 matches - and first at Bramall Lane since mid-December - in a punishing blow to their automatic promotion hopes.
Weimann cancelled out goals from Billy Sharp and substitute Scott Hogan, which had put the Blades in front twice, and then crowned a virtuoso performance by scoring a dramatic winner seven minutes from time.
It was the final act in a dramatic see-saw affair in which the Blades produced an uncharactetistically sloppy display - and failed to cash in on a strong start.
Following some warm-weather training in Valencia with some sun on their backs, the warm front continued for the Blades early on amid splendid spring sunshine in the Steel City.
A riproaring opening was crowned by a trademark early opener from Sharp, who produced a clinical header from John Fleck’s quality free-kick delivery with just six minutes on the clock, with the signs looking ominous for the visitors.
To their credit, they regrouped well after a fraught start with their passing game increasingly in evidence, with the Blades, by contrast, being uncharacteristically sloppy in possession.
The hosts were indebted to an impressive save from Dean Henderson to keep out Josh Brownhill’s long ranger, but he could do nothing about City’s leveller on the half-hour.
A dangerous cross from Jack Hunt, who looked the chief outlet down the right for the visitors, was latched onto by Andi Weimann, whose sharp header flew over Henderson.
Buoyed in confidence, City stroked the ball around nicely up until the interval, with the Blades - whose best moment after their opener saw David McGoldrick test the reactions of Max O’Leary with a fierce low drive - handed food for thought.
Bristol’s strong start to the second half provided further worries, with Henderson fielding low drives from Korey Smith and Weimann before the hosts - who brought on Hogan at the break for the quiet Kieran Dowell - started to produce some belated pressure.
John Fleck tested the reactions of O’Leary with a piledriver on the hour, with home supporters starting to increase the decibels in the stands too.
But the hosts were afforded a big let-off midway through the half when the impressive Brownhill saw his free-kick hit the post with Henderson motionless after Norwood was booked for a foul on Weimann, another who posed the Blades plenty of problems.
The magnitude of that moment was underlined not long after when the hosts scored a relieving second goal to go in front for the second time.
Pressure down the right saw George Baldock deliver an inviting hanging cross which was headed home in poacher’s fashion at the far post by Hogan.
It looked like being a pivotal moment, only for the visitors to stun the vast majority of the 30,030 crowd with a second leveller six minutes later.
The Blades were unhinged by a quality cross from substitute Kasey Palmer, with Weimann staying alert to stick out a leg and divert the ball past Henderson.
Weimann then added the salt in the hosts’ wounds with a fine strike to clinch his hat-trick, firing high past Henderson after a clever interchange with Diedhiou.
Sheffield United: Henderson; Basham, Egan, O’Connell (Johnson 76); Baldock, Norwood, Fleck, Stevens; Dowell (Hogan 45); McGoldrick, Sharp. Substitutes unused: Coutts, Stearman, Moore, Cranie, Washington.
Bristol City: O’Leary; Kalas, Wright (Palmer 73), Webster; Hunt, Brownhill, Smith (Paterson 73), Pack, Da Silva; Weimann (Baker 86), Diedhiou. Substitutes unused: Taylor, Kelly, Eliasson, Marinovic.
Referee: J Linington (Isle of Wight).
Attendance: 30,030 (1.363 Bristol City fans).