He was born of Latvian and English parentage, and spent his early life in Leicester, England.

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.

[2] In 1997, he qualified for the main stages of the World Championship, defeating Scott Rigg, Jason Wallace, Karl Payne, Jason Weston and Chris Small in qualifying, and was drawn to play Peter Ebdon in the first round.

[4] Having regained his professional status for 2008/2009 by winning the EBSA International Open in 2008,[2] he defeated Chris McBreen and David Roe before losing to Barry Pinches in the third qualifying round of the 2008 Bahrain Championship.

[5] Mazrocis' attempt to qualify for the World Championship in 2009 resulted in a 9–10 defeat to Tony Knowles in his first match.