Trefilov was drafted by the Calgary Flames 261st overall of the 1991 NHL Entry Draft (12th round) from the Dynamo Moscow. He would play one more season with the Dynamo before moving to North America in 1992-93; he made his NHL debuts in 1993-94 with the Flames, playing in 11 games, winning three of them, losing four and adding two ties; he however recorded an impressive two shutouts. Internationally, Trefilov wore the colours of his country at the 1991 Canada Cup, the 1991, 1992, 1993 and 1996 World Championship, the 1992 and 1998 Olympics, as well as the 1996 World Cup.