His debut came at the third attempt, having previously been an unused substitute on two separate occasions in the BKT URC in narrow wins over Scarlets and Connacht at Scotstoun.
Duncan then made his first start for Glasgow Warriors in the final match of the 2024/25 regular season, impressing at blindside with a physical display against Leinster at the Aviva Stadium.
He started the 2025/26 season in impressive fashion, claiming BKT URC Player of the Match honours in defeat to Benetton before scoring his first try for Glasgow a fortnight later in a bonus-point win over Ospreys.
The back-rower has previously represented Stirling Wolves in the FOSROC Super Series, as well as being included in the Scotland A squad that claimed victory over Chile in November 2024.