Remember the 6,000-plus, not the seven ... the story of Manchester City 7 Rotherham United 0

For 12 minutes, 6,000-plus Rotherham United fans dared to dream.

Then Manchester City took the lead and there was no way back for the Millers in the third round of the FA Cup.

Two quickfire goals killed the contest just before half-time and four more after the break didn't flatter the home side.

So good were their opponents that Rotherham couldn't muster an effort on target until they were 7-0 down, when a Michael Smith shot brought a save from Ederson.

Even City manager Pep Guardiola realised he'd watched something special. "Everybody was really, really good," he said.

City under Pep have hammered far bigger and better teams than the Millers.

The match pitted him against lookalike Paul Warne, two bosses going bald head to bald head, and Warne didn't try to hide from what had happened.

"I'm pleased the final whistle went," he said, "You don't know just how good and quick City are until you actually play against them.

"We had a few good passages at 1-0 down. I would have been pleased to get in at 1-0, but they scored twice and then it became about damage limitation

"Could I ask my lads to give more? No I couldn't. The gulf in class was evident. Their slowest player is quicker than my fastest one."

Rotherham town centre had emptied on Sunday morning, a convoy of coaches taking the sold-out hordes to watch their side take on the Premier League kings.

£390 million Manchester City versus a Rotherham team assembled at a cost of less than seven figures, record City signing £60m Riyad Mahrez against record Millers buy £500,000 Jon Taylor.

Rotherham wore sky-blue socks and, at times, it was as close as they could get to City.

The Millers never stopped competing, but Guardiola's men were too sharp and too slick whenever they pressed the accelerator.

Rotherham almost found themselves behind after just 71 seconds when Kevin De Bruyne dinked a perfect cross on the head of Gabriel Jesus only for the striker to direct an easy chance on to the bar.

Marek Rodak tipped away a Riyad Mahrez shot in the 10th minute and the City breakthrough came two minutes later when Raheem Sterling skipped inside from the left to fire in.

Ajayi had a shot deflected wide for the Millers but City suddenly stepped up the pace and scored twice in two minutes as the break approached.

Foden got on the end of Ilkay Gundogan's pass and was lucky when his miscontrol foxed Rodak, then Ajayi put the ball into his own net while trying to clear a Kyle Walker cross.

City were simply on another level. Of the team that had conquered Liverpool last Thursday, Ederson, John Stones and Sterling were selected again, augmented by the likes of Kevin De Bruyne, Jesus and the coming prince of English football, teenager Phil Foden.

The Millers fall behind

It was a side capable of beating any outfit in the Premier League except, maybe, City's own first 11.

In contrast, Rotherham, hit by injuries and a suspension for Richie Towell, were able to name only six substitutes.

"The lads can learn a lot from how good City were," Warne said. "I know the scoreline sounds depressing, but Premier League teams come here and get a good licking."

The last time the Millers had faced the top-flight champions in the FA Cup was in 1966 when the Manchester United team of George Best, Denis Law and Bobby Charlton were taken to a Millmoor replay and extra time before Matt Busby's side won 1-0.

There was no such parity at the Etihad and eight minutes after the break Jesus tapped in Sterling's cross to make it 4-0.

Rodak produced a superb 70th-minute stop to prevent a Zak Vyner own goal and when Riyad Mahrez increased the margin to five on 73 minutes Warne reacted by bringing on another defender, Sean Raggett, in a bid to halt the damage.

Rodak did well again, this time to thwart Walker, but from the corner Nicolas Otamendi headed home in the 79th minute and Leroy Sane added a seventh soon after.

For Pep's boys, it was just a routine passage to the fourth round against opposition from a division below. For Warne's men, it was their cup final going horribly wrong.

This was their heaviest ever defeat in the competition, eclipsing the 6-0 loss against Brighton & Hove Albion in 1960, and their worst result since a seven-goal third-tier mauling at Wrexham in 1995.

Warne made a point of saluting the bumper away contingent at the final whistle.

"The following was hugely impressive," he said. "I felt I had let them down a little bit, to be honest. I just wish we had scored a goal for them because the place would have gone crazy."

Millers fans had refused to be silenced. 'Stand up if you love Rotherham,' they'd chanted.

The home crowd responded with: 'Stand up for the champions.'

Stand up for City indeed. Different class. Also stand up for the 6,000-plus. Different class too.

City (3-4-3): Ederson; Kyle Walker, John Stones, Nicolas Otamendi; Oleksandr Zinchenko, Ilkay Gundogan, Phil Foden, Kevin De Bruyne; Riyad Mahrez, Gabriel Jesus, Raheem Sterling. Not used: Aro Muric, Aymeric Laporte, Bernardo Silva, Fernandinho.

Subs: Leroy Sane (for Sterling, 57 minutes), Philippe Sandler (for De Bruyne, 67), Danilo (for Stones, 75).

Rotherham (4-4-1-1): Marek Rodak; Zak Vyner, Semi Ajayi, Clark Robertson, Joe Mattock; Anthony Forde, Will Vaulks, Ben Wiles, Jon Taylor; Ryan Williams; Michael Smith. Not used: Lewis Price, Billy Jones, Joe Newell.

Subs: Sean Raggett (for Taylor, 74), Richard Wood (for Vyner, 89), Matt Palmer (for Williams, 89).

Goals: Sterling 12, Foden 43, Ajayi og 45, Jesus 53, Mahrez 73, Otamendi 79, Sane 85 (City).

Referee: David Coote (Nottingham).

Attendance: 52,708.