A highly-skilled player who possessed explosive skating ability, Klassen was touted by pro scouts as one of the top North American players in 1975, and was appropriately selected high in the two amateur drafts: 3rd overall in the first round of the 1975 NHL Amateur Draft by the California Golden Seals and 5th overall by the Cleveland Crusaders of the World Hockey Association (WHA) in the first round of the 1975 WHA Amateur Draft. When many drafted players of that year were signing unusually large contracts, opting to begin their careers in the fledgling WHA, Klassen chose a more traditional route, and signed his first pro contract with the California Golden Seals for US$70,000 per season.