Two moments of Manchester City class crushed Peterborough's growing hopes of an FA Cup giant-killing.
It was a classic cup match, despite being in midweek, with the Championship’s bottom club defying their lowly status to keep it goalless by halftime and then threatening to tweak the nose of the Premier League kings.
On a sticky, unpredictable pitch, it started to look like all the ingredients were there for a shock. But since Wigan got under their skin four years ago, City have clamped down on such embarrassments.
READ MORE: Fans react to Oleksandr Zinchenko captaining Man City
And for all of Posh’s industrious work in closing down and knocking City out of their accomplished stride, the unseen effects it was having on their legs proved telling.
The moment their level dropped, Phil Foden stepped up to provide the killer goals for Riyad Mahrez - a career-best 19th of the season - and Jack Grealish.
The 21-year-old, playing in the Kevin De Bruyne role, freed Mahrez on the right for the first and then produced the pass of the match, beautifully finished by Grealish, to finish Posh off.
Peterborough’s pitch fell apart last season after a drain burst, and they have worked hard to get it back in some sort of shape.
But after a few deluges lately, it has started to deteriorate again, and you suspect they were not desperate to sort it out too well ahead of slick-passing City’s visit - and who can blame them?
In a below-par first-half, the Blues attacked largely down the right, with Mahrez and Joao Cancelo working hard to work openings and deal with the threadbare patches in that corner.
The other side saw City at their most vulnerable.
Manager Pep Guardiola made the right call in not only playing Oleksandr Zinchenko but making him captain for the night, having noted that he is happier and distracted from the ills besetting his homeland when he has a football at his feet.
He led City out alongside Posh skipper Frankie Kent, the two men holding a Ukraine flag between them in a show of solidarity with the beleaguered nation.
But it seemed apparent from early in the game that Zinchenko’s mind was not entirely present, entirely understandable as he worries about family and friends who are facing the might of the Russian armed forces.
With Nathan Ake alongside him a centre back, Peterborough sensed an opportunity to exploit, and it almost paid off early in the game as they fashioned the first chance.
Jeando Fuchs sprinted into a yawning gap between the two and, after holding off a half-hearted challenge from Ake, shot low and hard, almost catching Ederson off guard at his near post - the big Brazilian threw down a hand and managed to turn it away from goal.
It was a warning for the Blues, and they poured forward in numbers and with some slick approach work, only for the final pass or shot to be closer to Championship standard than Premier League.
With Fernandinho establishing a steely grip inside a silken glove, and Ilkay Gundogan making a mockery of the tricky surface with some light-footed mastery, City were getting to the penalty area with ease, but - faced with a packed defence - could not find the final ball they needed.
They started to edge closer as the half wore on and Posh began to tire, as they worked hard on a heavy pitch.
Gundogan curled a shot narrowly wide and then missed the target with a header after he somehow contrived to find an unoccupied yard of space to get on the end of Mahrez’s cross.
Guardiola swapped his centre backs at halftime in what seemed to be a pre-planned move, but Peterborough continued to open them up down the City left, Sammie Szmodics scuffing his shot when a long throw-in fell invitingly to him, and then Foden bravely denying another great chance with a lunging tackle as Jorge Grant was lining up a famous goal.
Peterborough and their fans were sensing an upset, throwing themselves into every challenge and working prodigiously hard to close the Blues down. Just as that optimism started to peak, Mahrez struck.
Foden found him in the kind of space he relishes, and having escaped the mud patch that slowed him in the first-half, he skipped inside Hayden Coulson, threw him a step-over to open the chink of daylight he needed, and unerringly threaded his shot through the mass ranks of defenders and inside the far post.
With their noses in front, City weren't about to let it slip, and Foden started to pull the strings.
His arrowed pass picked out Grealish’s run, and the England man showed brilliant control and smartly stroked the ball past keeper Steven Benda.
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