Key takeaways: 

• Jack Grealish expresses the first FA Cup goal of his career was motivated by watching footage of Lionel Messi ere Manchester City's hard-earned victory over Peterborough United.
• Riyad Mahrez set the Premier League chiefs ahead with their first try on target before Grealish - the most costly British player of all time - packed City's position in the quarter-finals.

Jack Grealish and Mahrez sealed the City's win: 

The England midfielder delivered a quality first touch to get Phil Foden's wide pass from inside his half under rule before moving it past the keeper and into the net.

"What's amusing is that before the match, while we were on the coach on the route to the game, I was seated next to Phil, and we were scrolling through tapes of Messi," Grealish revealed ITV.

"After netting, Foden came up to me and told me it was just like we were watching."

The City was made to perform hard for their fifth-round victory.

At the base of the Championship, Peterborough should have grabbed the lead with the match goalless, but Sammie Szmodics grazed his shot, and Ederson rejected Jeando Fuchs.

Six-time champions City will see their rivals on Thursday.

Man City get the job accomplished

The City has now netted 103 goals in all contests this season.

But it needed two quality finishes - both assisted by Foden - in the room of seven second-half minutes to pack City's passage.

The City made six changes but still fielded a robust team, including replacing Ukraine defender Oleksandr Zinchenko, who was given the captain's armband in solidarity and backing.

Zinchenko's first match since Russia raided his homeland, and he held the Ukrainian flag on the field with Peterborough skipper Frankie Kent before kick-off.