Peter Cassilles joined Canterbury in 1973 as a lock forward.
Peter progressed through the grades quickly to play in the reserve grade Semi-Final against Newtown.
Peter became a regular member of the reserve grade team in 1974 and received the opportunity to play first grade against Western Suburbs as a replacement.
In 1975, Peter started the season in reserve grade but when Geoff Connell was injured, he spent the mid-season in first grade. Peter also played in the Preliminary Semi-Final against Parramatta as a replacement.
In 1976, Peter started in reserve grade but became a regular member of the first grade team when Graeme Hughes was injured. Unfortunately Peter was injured late in the season and missed the finals.