In both those years, 1940 and 1941, Port Melbourne were Victorian Football Association (VFA) premiers but Castles was only a member of the 1940 grand final winning team.
Mostly used at half forward and as a rover, Castles was a consistent source of goals for South Melbourne, finishing runner up in their goal-kicking on four occasions.
[3] In the premiership decider, where no less than six of Castles teammates were reported, he lined up on a half forward flank and kicked a club high three goals, in a losing side.
He was granted a clearance at the end of the season and returned to Tasmania, taking up the position of playing coach for Burnie in the North West Football Union.
[5] He was in charge of Burnie from 1948 to 1950 and his on field performances were rewarded with selection in the Tasmanian team which competed at the 1950 Brisbane Carnival.