Clarets legend Michael joined the Academy in the summer of 2016 after announcing his retirement following 383 appearances for the club.
The defender, who joined from Cheltenham Town for £30,000 in 2004, is the fourth oldest outfield player since the war in the club’s 134 year history.
His final game, in the Championship title winning game at Charlton Athletic in May, 2016, put him level with Adam Blacklaw in 13th place on Burnley's all-time appearance list.
Duff has played his part in three promotions to the Premier League. By winning the title, he now has a Play-off final, a runners-up and, fittingly, finally, a winners medal.