 As a youth, Cassivi played in the 1989 Quebec International Pee-Wee Hockey Tournament with a minor ice hockey team from Francheville, Quebec.Cassivi was originally drafted at the 1994 NHL Entry Draft in the 9th round, 210th overall, by the Ottawa Senators.Cassivi spent several years in the minors before signing with the Colorado Avalanche in 1999 as a free agent, although he would play primarily for their minor league affiliate the Hershey Bears.