United's second-string, sitting in fifth place on 14 points, face their Leeds counterparts at the Thorp Arch training ground (kick-off 1pm GMT), aiming to inflict a first defeat on the Whites who have won seven of their opening eight matches.
Barclay, who signed his first professional contract with his boyhood club last summer, is hopeful of a strong result against the current table toppers to continue their hunt for promotion.
The 18-year-old defender told nufc.co.uk: "We're on a good run of form at the moment and are very confident as a squad with the way we've played lately. We must be doing something right and we'll try to do everything we can to win the game.
"It will be a test but, like every game we play in, there's challenges in them. We need to compete with them, on and off the ball and make sure we are strong in their tackles and take any chances that come our way.
"We've seen in other games so far this season that anything can happen. Southampton were on a good run of form before they played us and we managed to beat them so it's just a case of another 11 players we will play against on Monday.
"It would give us a lot of confidence heading into the new year. We've still got games to play over the winter but a positive result against Leeds would put us in good stead for the Premier League Cup matches in December."
Competing in his first full season with Newcastle's under-21 side, Barclay has overcome two setbacks in the opening half of the 2022/23 campaign after sustaining a quadricep and achilles injury.
Featuring in the right-back role this term, Barclay - who joined the Magpies' academy in 2012 - has started the last three games at under-21 level and aims to add to his tally after overcoming his time spent on the sidelines.
The Ashington-born teenager, who made his under-21s debut at the age of 16, added: "I've enjoyed it. It's been full of ups and downs so far. I did well in pre-season but then I got injured in the penultimate match before the league season so I was out for four weeks.
"I was getting my fitness back, training again, before getting another injury. It was hard to deal with but being injured is part of football.
"Now I'm fully fit, it's good to be in the team and being picked to play. We're picking up results and I'm hoping to continue getting better and better each week."
