A heavyweight competitor fighting out of Montreal, Rivière reached the semi-finals at the 5th Kyokushin World Open in 1991 and later embarked on a career in the K-1 kickboxing promotion and the burgeoning MMA scene of the mid-1990s.
[2] Rivière would later transition to mixed martial arts, making his debut in Brazil on December 1, 1995 where he knocked out capoeira stylist Mestre Hulk in nineteen seconds.
In his first outing, he recorded a second round low kick stoppage win over Fred Floyd at K-1 Revenge '96 on September 1, 1996 before losing a five-round unanimous decision to Musashi at K-1 Star Wars '96 the following month.
Rivière was invited to compete in the 1997 K-1 World Grand Prix, losing to fellow karateka Masaaki Satake in the tournament's opening round on September 7, 1997.
Rivière faced reigning K-1 World Grand Prix champion Ernesto Hoost at K-1 Braves '98 on May 24, 1998, losing by head kick knockout in the first round.