Filby began his career in the youth system at Second Division club Orient and signed his first professional contract on his 18th birthday in October 1972.
[1] Filby moved to Canada to join North American Soccer League club Montreal Olympique on loan for the 1973 season.
[2] Manager Graham Adams commented that Filby was faster and had better ball control than the previous season's highly rated Scottish player Graeme Souness.
[2] Filby was loaned to Brentford, St Mirren and Romford during the 1974–75 season and departed Orient at the end of the campaign.
[2] Filby returned to North America to sign for American Soccer League club Sacramento Gold in 1979.