Born in Falmouth, Cornwall, Miller was a product of the Falmouth Town youth scheme playing mostly in midfield before being persuaded to take up goalkeeping in the Combination League team by then manager Keith Rashleigh as a 15 year old.
Miller's early career involved playing as a midfielder for Falmouth Town, but he later transitioned to goalkeeping after being persuaded by manager Keith Rashleigh when he was 15 years old.