Maguire turned professional as a snooker player in 1998. He qualified for the 1999 UK Championship before being defeated by Mark King 9–2. Maguire played in qualifying for the 2000 World Snooker Championship defeating Wayne Brown, Nick Walker and Bradley Jones to reach the final qualifying round. There he played Joe Swail, losing 9–10. At the 2002 UK Championship Maguire qualified again, going on to defeat Fergal O'Brien 9–4 in the first round before losing 7–9 to Ken Doherty in the second.