Jacey Carrick was given an opportunity to impress after United were left without at least 22 senior players because of international duty and injuries.
The midfielder, who has made five appearances for the Under-18s this season, came on during the friendly against Lausanne as Michael Carrick's side turned to several academy players.
Jacey joined Manchester United's academy aged six and signed his first-year scholarship contract with the club in July.
The teenager has grown up supporting United and has documented his progress through the academy, including youth tournament successes and his scholarship deal.
His connection with the club stretches back almost as far as his memory. Jacey was just one year old when he first appeared on the Old Trafford pitch during United's title celebrations in May 2011.
He and sister Louise later served as mascots when Carrick played what he believed would be his final United match against Bournemouth in May 2016.
Carrick had initially been told by Louis van Gaal that he would not receive a new contract, but Van Gaal's dismissal and José Mourinho's arrival changed the situation.
Jacey also accompanied his father onto the pitch following Carrick's testimonial at Old Trafford in 2017.
The youngster has developed a close friendship with Kai Rooney, the son of Wayne Rooney, after the pair came through United's academy together.
Carrick has previously described his son as being “United obsessed” and took him to his first away game at Burnley in January 2018.
On that occasion, Mourinho allowed Jacey into the dressing room while Carrick was recovering from a heart procedure. United went on to win 1-0 at Turf Moor.
Carrick later wrote in his 2018 book that he was proud of both Jacey and Louise, highlighting their character away from football.
The latest appearance represents another step for Jacey, who is still only 16 and remains at the beginning of his development.
His first-team debut came in unusual circumstances, with United's senior squad depleted by international commitments and injuries, but it nevertheless gives him an early taste of football at the highest level.
For a player who has spent almost his entire childhood inside the United system, appearing for the first team carries particular significance.