Under-fire Sheffield United boss Bryan Robson conjured one of the sweetest results of his career as the Blades took a second Premier League scalp in this season's FA Cup.

Former Manchester United captain Robson saw his side clinch a place in the fifth round after holding onto a first-half lead courtesy of goals from Luton Shelton and Jon Stead.

Rising teenage star Daniel Sturridge gave City hope with a stunning volley three minutes after his arrival as a half-time substitute, but United were barely troubled after that.

For Robson, the victory will have come as a major relief as there had been rumours this week his job was on the line following last weekend's 2-0 derby defeat at Sheffield Wednesday.

But if there was any suggestion his team did not want to play for him, that was blown away by this performance, and the first half in particular.

It will have had most United fans wondering just why their team has performed so miserably on occasions in the Championship this season.

But after the opening 45 minutes Robson's side were rewarded with a rousing reception as they left the pitch leading 2-0 against a strong City side flying high in the Premier League.

Even Robson must have chuckled to himself, though, at the comical nature of his side's first goal inside 12 minutes.

There had been little to separate the teams in the opening stages despite the fact Robson had made six changes to his team, including starting roles for Shelton and Stead.

The latter had come close in the ninth minute with a downward header onto a Shelton cross that had Joe Hart at full stretch.

But three minutes later a swift break down the left wing resulted in Lee Martin - on loan from Manchester United - delivering a low, piercing cross into the heart of the area.

The ball initially took a slight deflection off the leg of City captain Richard Dunne, and then onto one of the blue balloons floating around the area courtesy of the 6,000 City fans behind Hart's goal.

Michael Ball was clearly confused as he completely missed his attempt at a clearance, while Shelton was almost also deceived.

But the Jamaica international managed to steady himself and slip a simple six-yard shot past Hart for only his third goal for the club following a £1.85million move from Helsingborgs a year ago.

An infuriated Hart then proceeded to stamp on and burst all the remaining balloons in his area, as well as the majority behind his goal.

City were also similarly fired up as they had three chances for an equaliser prior to Stead doubling United's lead in the 24th minute.

Initially, a fit-again Emile Mpenza - in the side after a six-week lay-off with a hamstring injury and replacing Rolando Bianchi who joined Lazio on loan this week - planted a free header over the crossbar from eight yards.

Then Elano struck the left-hand post with a right-foot shot from 20 yards, and followed up shortly after with a curling free-kick that kicked up off the turf, only for Paddy Kenny to pull off a sensational one-handed save.

The Blades then made it 2-0 to the unbridled joy of Robson on the touchline.

This time the goal stemmed from the right wing and a cross from Derek Geary the City defence struggled to clear, with the loose ball falling for Stead to drive home from 12 yards.

United managed to see out the remainder of the half without too much threat from their opponents, only to be caught out by a slice of magic from City's up-and-coming striker Sturridge.

The 18-year-old replaced Elano - who had grown in frustration as the first period wore on - and within three minutes of his first appearance of the season he was on the scoresheet.

Eriksson raved about the youngster - nephew of former Derby and Wolves striker Dean - in Friday's pre-match press conference, and it was easy to see why.

Sturridge, who scored a hat-trick in City's 3-1 FA Youth Cup win over Reading on Wednesday, was in the right place to take a ball that had skimmed off the head of a falling Dunne from a Corluka corner.

Showing the composure of a veteran, he then knocked the ball up with his right knee before volleying home from 15 yards with his left foot.

That should have been the cue for City to mount a comeback, but not once did they manage to test Kenny again, allowing United to take their place in the last 16 with ease.

Teams

Sheff Utd Kenny, Geary, Bromby, Morgan, Naysmith, Gillespie,Speed, Martin, Quinn, Shelton (Tonge 76), Stead (Sharp 49).

Subs Not Used: Hendrie, Kilgallon, Armstrong.

Booked: Martin, Quinn, Morgan.

Goals: Shelton 12, Stead 24.

Man City Hart, Corluka, Onuoha, Dunne, Ball,Elano (Sturridge 46), Hamann (Ireland 62), Gelson, Petrov,Mpenza (Geovanni 71), Vassell.

Subs Not Used: Schmeichel, Jihai.

Booked: Gelson, Corluka.

Goals: Sturridge 48.

Att: 20,800

Ref: Alan Wiley (Staffordshire).