Boss Michael Duff believes Cheltenham would make FA Cup history if they pulled off a monumental shock against Manchester City.

The Robins face City for the first time in the fourth round on Saturday.

The Cup mismatch sees the Sky Bet League Two promotion-chasers sit 72 places below six-time winners City.

Pep Guardiola's Premier League giants head to the Jonny Rocks Stadium unbeaten in 16 games in all competitions – having not conceded in their last five – and Duff knows the task Cheltenham face.

"This would be the biggest upset in cup history, just because of their dominance against Premier League teams," he said.

"One of their players' wages for the week would probably pay our whole payroll for a couple of months but that's football. There are always the haves and the have nots.

"Their form has been off the charts. You need a lot of luck, players to play out of their skin and Man City to have a real off day.

"I've been both ends of the spectrum against Manchester City in the Premier League. We (Burnley) beat them 1-0 (in 2015), when they were champions, but I've also been 3-0 down after six minutes and 5-0 down at half-time.

"The game should have been called off because of the weather but nobody in Burnley wanted it off because we didn't want to go through that chasing again and we lost 6-1.

"It was a massive shock when we beat them and we were in the same league."

Duff is realistic but insisted the Robins will do all they can to make Guardiola's side comfortable and will not try any tricks to gain an edge.

"They'll be getting changed in a bar, we'll make it as hospitable as we can and the one thing they will like is the pitch. You are not going to get a Ronnie Radford scene where it's a ploughed field," he said.

"They will be able to play on it – we won't be training on it to make it as bad as possible.

"We do pride ourselves on playing good football, we are not going to ruin the pitch for this one-off."

As well as his playing career there is a personal connection for Duff, who lived in Manchester during his 12 years at Burnley after joining from Cheltenham in 2004.

Sons Tommy and Jack were both born there with Tommy, 12, a City fan while Jack, 10, supports Manchester United.

"It's a double-edged sword, they are buzzing for the game but gutted they can't be there," he said. "They are both Mancs, they are not glory hunters. You can see Old Trafford from the room they were both born in.

"One has decided City and one has decided United. They are on online school lessons and meetings and that's all they talk about, we just hope the club can do them proud."

Duff is also confident goalkeeper Josh Griffiths can recover from conceding a freak goal against Newport.

Tom King's wind-assisted goal kick – now recognised as a world record for the longest goal scored – bounced in during the 1-1 draw on Tuesday but Duff believes the 19-year-old, on loan from West Brom, will be fine facing City.

He said: "One of Josh's strongest attributes is his mentality. A lot of young goalkeepers are anxious, want to get involved and show how good they are.

"It doesn't happen very often, but unfortunately it's happened to him. That's why he's here, to make those mistakes for us rather than his parent club so that when he goes back, hopefully it won't happen again."