 Mazrocis turned professional in 1991.In 1995, he qualified for the main stages of the World Championship at the Crucible Theatre, defeating Lee Walters, Martin Dziewialtowski, Jason Prince, Scott MacFarlane and Mark Bennett; drawn against incumbent champion Stephen Hendry in the last 32, he lost 3–10.Two years later, he repeated this feat, overcoming Scott Rigg, Jason Wallace, Karl Payne, Jason Weston and Chris Small in qualifying, and was drawn to play Peter Ebdon in the first round.