City had been knocked out by a Championship side in each of the last two seasons but any suspicions that Roberto Mancini's team might not have the stomach to see off another ambitious underdog on a damp and murky afternoon in Lincolnshire were dispelled, in the end, quite emphatically, earning a home tie with Stoke City in the fifth round of the FA Cup.
With Arsenal put out by Stoke yesterday and Manchester United already gone, the Italian sees a chance to win silverware in this competition. "There is still Chelsea, Aston Villa and maybe Tottenham, some good teams," he said. "Stoke will be a hard game but there is a possibility for us."
Doughty Scunthorpe, fighting for survival in the second tier, were good enough to equalise after slipping behind early in the game and came back a second time to trail 3-2 with 20 minutes left. But their manager, Nigel Adkins, was quick to acknowledge the Premiership side's sure-footed performance.
"We thought there might be a giant-killing in the offing and we gave it our best shot," he said. "But you can't intimidate them. They are just too professional."
They were put in their place ultimately by the least likely figure as Robinho, making what is widely tipped to be the farewell appearance of his largely forgettable time as a City player, signed off with their fourth goal, before being immediately substituted.
There was no doubt this was a tie with banana skin potential. Scunthorpe, who would never pretend to be anything but a small club, were in League One last season and their Glanford Park ground holds only 9,000 spectators. But they sit close to the narrow pitch and in the misty chill of yesterday afternoon there was no mistaking which was the away side.
Yet City, who made eight changes from the XI that took a step towards Wembley in the Carling Cup last week, were ahead even before the home crowd had anything to be excited about. Robinho's extravagant stepovers outside the Scunthorpe penalty area seemed a little pointless but when, eventually, he sent the ball left, Martin Petrov went past Garry Thompson in a blur before lashing a left-foot drive between the angle of post and bar as keeper Joe Murphy flapped helplessly.
It was not good defending, but Scunthorpe put it behind them quickly and went about their business with no sign of panic. They had been thumped 5-1 at Eastlands in the Carling Cup last November but there was no Carlos Tevez to worry about, the Argentine getting the day off ahead of Wednesday's return semi-final against Manchester United, while Craig Bellamy and Shaun Wright-Phillips started on the bench and their plan to press City in their own half paid off.
They were close to pulling level after a quarter of an hour, squandering two chances that seemed unmissable. Cliff Byrne somehow headed against the bar when a Gary Hooper cross found him unmarked at the far post, then Paul Hayes scuffed wide from close range as the City defence continued to wobble.
But persistence gained its reward in the 29th minute. When Martyn Woolford, whose father and grandfather both played professional rugby league, hoisted an up-and-under as City's back four pushed out, Hayes was deemed to be onside as the ball dropped and his volley gave the debutant City keeper Stuart Taylor no chance.
City struck again in the dying moments of the half, full-back Nedum Onuoha slipping behind their defence to pick up a clever pass from Stephen Ireland and restore their lead. Eight minutes into the second half, only a fingertip save from Taylor against Sam Togwell denied Scunthorpe a second equaliser, but when Silvinho's superb dipping shot from 30 yards provided City with a third goal, Mancini's passage to the fifth round looked assured.
The Italian knows something of the passion of the FA Cup, however, and he was not surprised that Scunthorpe would not lie down. Murphy kept them in the hunt with a triple save and after Byrne's shot found the net via a deflection off Dedryck Boyata, City faced potentially a tough last 20 minutes.
Yet the home side could not summon up the storming finish they wanted and instead, as City imposed their quality, Petrov set up Robinho for an effortless final goal and a parting celebration in front of the travelling fans.
Scunthorpe United (4-4-2): Murphy; Byrne, Jones (Milne, 82), Mirfin, Williams; Thompson, McCann (Wright, 88), Togwell, Woolford; Hayes (Forte, 88), Hooper. Substitutes not used: Lillis (gk), Sparrow, May, Crosby.
Manchester City (4-3-3): Taylor; Onuoha, Boyata, Kompany, Sylvinho; Ireland (Zabaleta, 66), De Jong (Cunningham, h-t), Ibrahim; Robinho (Bellamy, 85), Benjani, Petrov. Substitutes not used: Nielsen, Richards, Wright-Phillips, Barry.
Referee: K Friend (Leicestershire).
Booked: Manchester City Cunningham.
Man of the match: Petrov.