Lyle Taylor’s second goal since joining on loan from Nottingham Forest opened the scoring in the second half before the Blades turned the game around thanks to goals from Billy Sharp and Jayden Bogle.
Home supporters voiced their anger at the running of the club, with sections of fans wearing masks as part of their ‘faceless’ protest and blowing whistles in the opening 10 minutes. Despite the troubles off the field, Lee Bowyer’s men had the better of the chances in the first half, with Kristian Pedersen and Onel Hernandez failing to hit the target from close range.
United thought they should have had a penalty in the first period when Iliman Ndiaye went down following a collision with Teden Mengi, but referee Keith Stroud instantly waved away the protests from the French forward.
After good work from Sharp and Sander Berge outside the box, the ball was slipped through for John Fleck, but his strike was blocked well by Pedersen.
Birmingham, who were unbeaten in their previous three going into the contest, broke the deadlock on the hour mark courtesy of their two recent signings.
Juninho Bacuna’s delicate flick in the middle of the park opened up the space and he was able to pick Taylor out on the left, with the forward taking his time before slotting past Wes Foderingham.
However, Paul Heckingbottom’s men levelled the scoring three minutes later. Fleck’s good work on the left made space in the middle for Berge to roam free into the Birmingham half.
The Norway international slotted the ball behind Blues’ defence and striker Sharp was there to slide in his ninth goal of the season and 15th goal involvement in 27 games.
United’s equaliser saw an increase in their tempo and they should have gone ahead when Fleck received the ball on the edge of the area.
A hopeful ball over the Blues defence was not dealt with by Pedersen and Ndiaye cut the ball back to Fleck, but his shot lacked conviction and was easily gathered by Neil Etheridge.
Heckingbottom’s side completed the turnaround in the 75th minute through Bogle’s third goal of the campaign.
A neat interchange of passes including Berge, Sharp and Bogle resulted in the right-back poking the ball under Etheridge from close distance.
Blues boss Bowyer received a yellow card following the goal after he expressed his outrage at the officials’ failure to penalise what he deemed to be an offside offence prior to the winner.
Birmingham: Etheridge, Colin, Mengi, Roberts, Pedersen, Woods, Bacuna, Hernandez (Graham 83), Gardner, Hogan (Jutkiewicz 83), Taylor. Unused substitutes: James, Trueman, Sunjic, Bellingham, Campbell.
Sheff Utd: Foderingham, Basham, Egan, Ben Davies, Bogle, Berge, Norwood, Fleck, Norrington-Davies, Ndiaye (McBurnie 78), Sharp (McGoldrick 89). Unused substitutes: Adam Davies, Baldock, Hourihane, Goode, Jebbison.
Referee: K Stroud (Hampshire).