Adam Rooney scored twice as Birmingham sealed their passage to the FA Cup fifth round with a comfortable victory over Sheffield United.
Highly rated 17-year-old Nathan Redmond fired in from the edge of the area following Jordon Mutch's corner.
Adam Rooney doubled the lead before half-time from Chris Burke's cross.
Although the Blades hit the woodwork, Wade Elliott sealed it from 20 yards when his shot was deflected in, with Rooney adding his second late on.
Despite the eventual margin of victory, the hosts had started strongly with Ched Evans twice going close and they also threatened briefly after half-time.
- Wade Elliott was on target against the Blades when Burnley beat them 1-0 in the 2009 Championship play-off
Yet once Redmond had put the visitors ahead, they never looked back.
Rooney's first goal gave Birmingham breathing space although, after the restart, Lee Williamson hit the bar and Lowton's follow-up effort bounced back off the post.
But the League One side's first defeat in nine home games was ensured when Elliott rifled home, with Rooney turning in David Murphy's cross to add the gloss.
Chris Hughton's side, who are sixth in the Championship, have now gone nine games unbeaten.
Birmingham manager Chris Hughton:
"It was a real good all-round performance. I'm as delighted with the clean-sheet and the performance as I am with the goals.
"They were certainly a threat but then we got into our rhythm and the timing of our goals was important.
"We're enjoying playing football and that breeds a certain amount of confidence."
Sheffield United manager Danny Wilson tells BBC Radio Sheffield:
"The score line wasn't a 4-0, we appreciate that, but we are still out of the cup.
"But we don't take too much disappointment from the performance, the result was that because they produced better clinical finishes in situations that they had better than we did when we had those situations and obviously that's the difference between the quality of the two teams.
"If you look at the first three goals we are in the ascendancy. We're pushing the game and all of a sudden we've been hit by the sucker punch.
"The first goal from the corner, it's a bit of quick thinking from their point of view and slow thinking from ours, but prior to that corner we're pushing very hard to get that first goal and that would have made the big difference, as it did."
- 01 Simonsen
- 02 Lowton
- 03 Lescinel (Williams - 60' )
- 15 Collins
- 19 Maguire
- 08 Doyle
- 14 Williamson
- 27 McDonald Booked
- 28 Quinn (Flynn - 72' )
- 09 Evans
- 17 Cresswell (Porter - 72' )
- 25 Long
- 06 Ertl
- 30 Williams
- 04 Montgomery
- 11 Flynn
- 22 Philliskirk
- 21 Porter
- 13 Doyle
- 03 Murphy
- 04 Caldwell
- 23 Spector
- 24 Davies
- 07 Burke (Gnahore - 80' )
- 12 Mutch (Reilly - 80' )
- 14 Gomis
- 15 Elliott Booked
- 22 Redmond
- 17 Rooney
- 26 Butland
- 05 Pablo
- 18 Fahey
- 20 Valles
- 34 Gnahore
- 35 Reilly
- 19 Zigic
Live Text Commentary
Full Time The match has reached full-time.90:00 +2:02
Ryan Flynn fouled by Jonathan Spector, the ref awards a free kick. Direct strike on goal from the free kick comes in from Lee Williamson, Colin Doyle makes a save.90:00 +1:04
Free kick awarded for a foul by Ched Evans on Wade Elliott. Free kick taken by Colin Doyle.90:00 +0:46
Foul by Wade Elliott on Marcus Williams, free kick awarded. Michael Doyle restarts play with the free kick.90:00 +0:04
Harry Maguire challenges Morgaro Gomis unfairly and gives away a free kick. Steven Caldwell takes the direct free kick.89:39
The ball is sent over by Matthew Lowton, clearance made by Curtis Davies.89:09
Inswinging corner taken by Ryan Flynn from the left by-line, Steven Caldwell makes a clearance.88:42
Morgaro Gomis concedes a free kick for a foul on Ryan Flynn. Matthew Lowton takes the free kick.88:05
Kevin McDonald takes a shot from just inside the penalty box which clears the crossbar.87:32
The ball is swung over by Lee Williamson, Ched Evans takes a shot. Blocked by Callum Reilly. Corner taken right-footed by Ched Evans from the left by-line, clearance by Steven Caldwell.84:58
Ryan Flynn crosses the ball, blocked by David Murphy. Corner taken short by Ryan Flynn.84:19
Foul by David Murphy on Ched Evans, free kick awarded. Lee Williamson crosses the ball in from the free kick, Adam Rooney makes a clearance.83:14
The referee blows for offside against Chris Porter. Colin Doyle takes the free kick.80:54
Free kick awarded for a foul by Wade Elliott on Ryan Flynn. The free kick is swung in right-footed by Lee Williamson, Curtis Davies makes a clearance.79:56 Booking
Booking Wade Elliott goes into the referee's book for unsporting behaviour.79:36 Substitution
Substitution Jordon Mutch leaves the field to be replaced by Callum Reilly.79:36 Substitution
Substitution Eddy Gnahore is brought on as a substitute for Chris Burke.78:57
Jordon Mutch takes the direct free kick.78:57 Booking
Booking Booking for Kevin McDonald for unsporting behaviour.78:49
Kevin McDonald gives away a free kick for an unfair challenge on Jordon Mutch.
Assist by David Murphy.77:46 Goal scored
Goal! - Adam Rooney - Sheff Utd 0 - 4 Birmingham Goal scored by Adam Rooney from inside the six-yard box to the bottom right corner of the goal. Sheff Utd 0-4 Birmingham.76:15
The ball is swung over by Lee Williamson, clearance by Steven Caldwell.74:40
The ball is sent over by Ryan Flynn. The ball is sent over by Matthew Lowton, clearance by David Murphy.73:08
The referee blows for offside against Harry Maguire. Colin Doyle restarts play with the free kick.72:28
Harry Maguire fouled by Wade Elliott, the ref awards a free kick. Free kick taken by Matthew Lowton.71:35 Substitution
Substitution (Sheff Utd) makes a substitution, with Chris Porter coming on for Richard Cresswell.71:35 Substitution
Substitution Stephen Quinn goes off and Ryan Flynn comes on.69:44
Matthew Lowton crosses the ball, Steven Caldwell makes a clearance. Inswinging corner taken left-footed by Stephen Quinn from the right by-line, Colin Doyle makes a save.66:09
Centre by Chris Burke, clearance by Matthew Lowton.65:09
Free kick awarded for a foul by Marcus Williams on Chris Burke. Free kick taken by Jonathan Spector.64:41
The ball is swung over by Matthew Lowton, save by Colin Doyle.63:19
The assistant referee flags for offside against Ched Evans. Colin Doyle takes the free kick.61:15
Chris Burke concedes a free kick for a foul on Stephen Quinn. Free kick taken by Harry Maguire.60:35
The ball is sent over by Wade Elliott, clearance by Matthew Lowton. Corner taken by Jordon Mutch from the left by-line, Richard Cresswell makes a clearance.59:48 Substitution
Substitution Marcus Williams on for Lecsinel Jean-Francois.59:10
Richard Cresswell crosses the ball, Steven Caldwell gets a block in. Stephen Quinn takes the inswinging corner, Curtis Davies makes a clearance.57:58
The assist for the goal came from David Murphy.57:58 Goal scored
Goal! - Wade Elliott - Sheff Utd 0 - 3 Birmingham Wade Elliott scores a goal from just outside the area to the bottom right corner of the goal. Sheff Utd 0-3 Birmingham.57:35
Adam Rooney sends in a cross, clearance made by Matthew Lowton.56:08
Harry Maguire has a drilled shot. Blocked by Curtis Davies.54:54
The ball is swung over by Chris Burke, Matthew Lowton manages to make a clearance.53:49
A cross is delivered by Richard Cresswell, clearance by Curtis Davies.52:53
Stephen Quinn takes the inswinging corner, Shot from close in by Richard Cresswell misses to the left of the target.52:17
Shot from 12 yards from Lee Williamson. Matthew Lowton takes a shot.51:08
A cross is delivered by Stephen Quinn.49:07
Lecsinel Jean-Francois challenges Chris Burke unfairly and gives away a free kick. Colin Doyle takes the direct free kick.47:04
Free kick awarded for a foul by Curtis Davies on Richard Cresswell. Free kick taken by Stephen Quinn.46:05
Richard Cresswell is flagged offside by the assistant referee. Colin Doyle restarts play with the free kick.45:01
The referee gets the second half started.45:00 +1:08 Half time
Half Time The referee blows for half time.44:05
Jordon Mutch challenges Stephen Quinn unfairly and gives away a free kick. Neill Collins restarts play with the free kick.40:54
Chris Burke produces a right-footed shot from outside the box and misses left.40:01
Wade Elliott sends in a cross, blocked by Lecsinel Jean-Francois. Outswinging corner taken right-footed by Jordon Mutch, Matthew Lowton makes a clearance.38:57
Ched Evans delivers the ball.37:19
The assist for the goal came from Chris Burke.37:19 Goal scored
Goal! - Adam Rooney - Sheff Utd 0 - 2 Birmingham Adam Rooney fires in a goal from close range to the top right corner of the goal. Sheff Utd 0-2 Birmingham.37:15
The ball is swung over by Chris Burke,36:26
Lee Williamson challenges Jordon Mutch unfairly and gives away a free kick. Jordon Mutch takes the direct free kick.33:27
Wade Elliott sends in a cross.33:13
David Murphy sends in a cross.31:13
Ched Evans produces a right-footed shot from long range which goes wide right of the goal.30:38
Nathan Redmond produces a right-footed shot from long range which goes wide right of the goal.29:43
Lee Williamson concedes a free kick for a foul on David Murphy. Colin Doyle restarts play with the free kick.28:23
Corner taken by Jordon Mutch from the right by-line, Richard Cresswell manages to make a clearance. Adam Rooney gives away a free kick for an unfair challenge on Richard Cresswell. Steve Simonsen takes the direct free kick.26:18
Free kick awarded for an unfair challenge on Richard Cresswell by Steven Caldwell. Strike on goal comes in from Ched Evans from the free kick, comfortable save by Colin Doyle.25:38
Wade Elliott challenges Stephen Quinn unfairly and gives away a free kick. Free kick taken by Lecsinel Jean-Francois.21:34
Effort from outside the box by Nathan Redmond goes wide right of the target.19:25
The referee blows for offside against Richard Cresswell. Colin Doyle takes the free kick.17:36
Assist on the goal came from Jordon Mutch.17:36 Goal scored
Goal! - Nathan Redmond - Sheff Utd 0 - 1 Birmingham Nathan Redmond grabs a goal from the edge of the penalty area low into the middle of the goal. Sheff Utd 0-1 Birmingham.17:03
Chris Burke sends in a cross, blocked by Lecsinel Jean-Francois. Outswinging corner taken right-footed by Jordon Mutch,16:50
Chris Burke crosses the ball, clearance by Matthew Lowton.15:09
Centre by Wade Elliott, Matthew Lowton manages to make a clearance.13:35
Jonathan Spector delivers the ball, clearance by Neill Collins. Jonathan Spector produces a right-footed shot from the edge of the box and misses to the right of the goal.12:10
Jordon Mutch concedes a free kick for a foul on Stephen Quinn. Stephen Quinn takes the free kick. Ched Evans has a drilled shot. Save by Colin Doyle.10:08
Ched Evans is flagged offside by the assistant referee. Colin Doyle takes the indirect free kick.7:31
Free kick awarded for an unfair challenge on Ched Evans by Morgaro Gomis. Free kick crossed right-footed by Lee Williamson from right channel, Curtis Davies manages to make a clearance.6:00
The offside flag is raised against Ched Evans. Free kick taken by Steven Caldwell.5:05
Matthew Lowton produces a cross, save by Colin Doyle.4:37
Lee Williamson produces a cross, blocked by David Murphy.4:30
Lecsinel Jean-Francois sends in a cross.3:19
The ball is sent over by Matthew Lowton, Shot by Kevin McDonald. Curtis Davies gets a block in.2:31
Free kick awarded for a foul by Adam Rooney on Matthew Lowton. Steve Simonsen takes the direct free kick.2:09
Stephen Quinn sends in a cross, save made by Colin Doyle.0:00
The referee gets the match started.
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