A striker, Valentine began his pro career in 1976 as a 17-year-old with Football League Second Division side Oldham Athletic.

Valentine signed with the Vancouver Whitecaps and as a rookie helped them win their only North American Soccer League championship in 1979.

[5] In June 1990, Valentine signed a one-year contract with the Blast only to be traded to the Kansas City Comets in exchange for Dale Mitchell on 21 August 1990.

He decided in 1985 however to declare his allegiance to his new home country and made his debut for Canada in a September 1985 FIFA World Cup qualification match against Honduras.

Despite a bad case of influenza, Valentine famously assisted on both goals (with corner kicks) Canada scored to defeat Honduras 2–1 to advance to the World Cup Finals for the first time.