Maguire has a rivalry with Shaun Murphy. In a match at the 2004 Grand Prix Murphy was involved in having one of Maguire's frames forfeited. As the match was about to begin, Maguire realised he had forgotten to bring his chalk with him. He asked referee Johan Oomen for permission to leave the arena. While he was away, Murphy spoke to the referee; the tournament director Mike Ganley was summoned, and he docked Maguire a frame for not being ready to start at the scheduled time. Maguire later won the match 5–2. Later that year, whilst playing in the final of the UK Championships, David Gray forgot his chalk. However, Maguire let him get it without a frame being docked. After beating Murphy in the 2007 Welsh Open, Maguire said, "That put the icing on the cake, but we've always had a rivalry. I dislike him and I think he dislikes me. I try hard to beat everyone, but it would have hurt more if I'd lost to him."