The 28-year-old defender, from Durrington, was part of the League Two County side to record a 2-0 fourth round replay win over Championship promotion-chasers Middlesbrough at Rodney Parade on Tuesday.
There was an added incentive for both teams going into that tie knowing Pep Guardiola's men were waiting in the next round.
And it was the former Worthing, Bognor and Eastbourne Borough defender Demetriou's Welsh side that came through to secure a dream fifth-round date with Man City.
But the Durrington-born defender has made it clear Newport will not be content with just rubbing shoulders with Sergio Aguero, Raheem Sterling, Kevin De Bruyne and co.
Demetriou has the belief the County can halt City's quadruple charge and secure a spot in the quarter-finals.
Michael Flynn's men have beaten higher-league opposition in Walsall, Leeds United and former Premier League champions Leicester City at Rodney Parade over the past two seasons in the competition.
They were also minutes away from toppling Tottenham Hotspur at home last term before bowing out in a Wembley replay.
Now Demetriou wants Newport to draw on those experiences and complete their biggest FA Cup upset of all.
He said: "We’ve got nothing to fear.
“We’re not expected to win so we can just go out, enjoy ourselves and see what happens.
“If we go out and give an account of ourselves and lose the game then everyone is going to be expecting that.
“As long as put a good performance in, who knows?
"They’re used to pristine pitches but they’ll come down to Rodney Parade and it’s like a rugby team has played on it.
“It could suit us as they may try to do things they’re not used to and we could adapt to that better than they can.
“We’ve got to go out and enjoy ourselves. We’ve done the club proud, everyone keeps telling us that, and it’s s free shot at trying to get through to the quarter-finals.
“You never know what can happen, strange things happen in football.
“As long as we ourselves proud, that is the most important thing.
“We’re playing against one of the best teams in the world."
Demetriou believes Newport getting a home draw is another advantage.
The Exiles have only lost two of 14 League Two home matches this season and their last FA Cup defeat at Rodney Parade came in 2016.
Tickets are expected to sell out quickly and Demetriou hopes the atmosphere can prove a telling factor.
He said: "The last couple of years we’ve beaten teams from leagues above us at home.
"There will be another sellout for the game against Manchester which is an extra help. The support is like having an extra player out there.
“The Middlesbrough players probably were expecting the atmosphere to be as good as it was. Hopefully it can be the same against Man City."
Although Newport's focus cannot switch to the Premier League champions just yet.
Flynn's troops, currently 14th in League Two, host Mansfield Town on Saturday before MK Dons visit on Tuesday leading into the FA Cup fifth-round clash.
Having those games is viewed as a positive by defender Demetriou.
Not only can County close the ten-point gap between themselves and the play-off places but the centre-back feels confidence can be built and starting places against Man City could be secured.
"We’ve got two massive league games to come first and then we can look forward to it," Demetriou said.
"As hard as it is we’ve got to put the Man City game to the back of our minds then come Tuesday night we can look forward to it.
“If we take our minds of these next two games we could damage ourselves and the league is our bread and butter.
“The FA Cup comes and goes. We have done well in that this year but we want to be fighting at the right end of the table.
“We want to go into the Man City game with momentum as well, we don’t want to be going into off the back off some bad league results.
“If we can go into it with a couple of good results the confidence will be flying then.
"We all need to perform well in the next two games to get the opportunity to play against Man City."
Demetriou's parents, best friend and Orchards Junior School teacher Owen Cave along with other family and friends are expected to make the trip up to see the tie.
The fifth-round clash will be broadcast live on BT Sport on Saturday week (5.30pm).
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