The 28-year-old from Durrington plays for League Two Newport County and they travel to Championship high-flyers Middlesbrough in the FA Cup fourth round.
Demetriou, who enjoyed spells at Worthing, Bognor and Eastbourne Borough early in his career, starred in central defence as Newport beat Leicester 2-1 at home in the third round, live on BBC.
Newport also caused a shock last season when they beat Championship side Leeds 1-0 in the FA Cup, before they gave Tottenham Hotspur a huge scare and only a late Harry Kane goal earned the Premier League side a replay, which Spurs won 2-0.
Demetriou began his career with Worthing and on the victory over Leicester, Premier League champions in 2016, he said: “To beat a Premier League team in the FA Cup was a huge result for us as a club and for us as lads.
“No one expected it and we were the shock of the round. It was nice to be a part of and it was up there with the best results we’ve had.
“They were Premier League champions three years ago and a lot of their players were Premier League winners and the other ones were bought for millions of pounds.”
Middlesbrough are next up at the Riverside Stadium for Newport and Demetriou said: “They’re a big club. You obviously want to get another Premier League team to see if you can do it again but it’s probably one of the better games if we didn’t get a Premier League team.
“It’s still a big game and everyone is looking forward to going up there this weekend and trying to cause another upset.”
Asked what Newport have to do to have a chance of causing another cup shock, Demetriou said: “We’ve got to put the same effort and same level of performance in as we did against Leicester.
“They’ve spent money to try to get back to the Premier League. We have to go there, not worry about that and try to enjoy the occasion and play our normal game. The most important thing is to play the game and not the occasion.
“If it comes off again, then we’ll be buzzing.
“We’re not the favourites, so it’s a free weekend for us.
“The pressure is off us and we can go and enjoy the occasion and try to win the game or get a result and bring them back to Rodney Parade.”
Demetriou’s Newport contract runs out this summer and he is keen for the club to finish the league season strongly as he bids to earn a new deal.
County are 13th in League Two, five points off the play-off places, and Demetriou said: “It’s nice to have this FA Cup run but the most important thing for us is the league. That’s our bread and butter and hopefully we can get ourselves back up the table.
“My contract runs out this summer and I’ve got to be playing well to try to earn a new one, whether it’s with Newport that’s down to the manager or whether it’s earning something somewhere else.
“A lot of the lads are in the same boat and we’ve got to make sure we’re playing well first and foremost for Newport County. Hopefully that will get us at least into the play-offs.”
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