Casey was part of Joe Antonelli’s Under-15s side which won the U15 National Floodlit Cup in 2022/23 against Stoke City, scoring in both the 3-1 win over the Potters and the 5-0 regional final victory over Arsenal.
He made his first appearance for Rob Quinn’s Under-18s in the U18 Premier League Cup semi-final against Manchester United on 2nd March 2024, marking a rapid step up to the age group. A week later, he opened his account against Arsenal before following that up with a brace against Norwich City.
The striker finished the 2023/24 campaign with seven goals in 11 appearances.
In July 2024, Casey signed a scholarship ahead of the 2024/25 season and continued his development with a strong first year at the level. He registered 12 goals and one assist, while also becoming the only player in the U18s squad to feature in all 28 matches across all competitions.
The 2025/26 campaign proved to be a breakthrough season, with Casey netting an outstanding 19 goals in just 18 appearances across all competitions for the U18s. He recorded multiple braces and two hat-tricks, while also boasting the best minutes-per-goal ratio in the U18 Premier League South at 74.
His goalscoring form was instrumental in Palace reaching their first FA Youth Cup semi-final in nearly 30 years, as well as securing the club’s maiden U18 Premier League Cup triumph.
One of his defining moments came in the Premier League Cup Final against Manchester United, where he won and calmly converted a dramatic 94th-minute penalty to force extra time. The young Eagles went on to hold their nerve in the shootout to secure historic silverware in front of 4,000 supporters at Selhurst Park.