Gray made his televised debut at the 2003 UK Open. He only began playing darts at the age of 18, and within three years had defeated notable players such as three-time world champion John Part.

He made his debut in the PDC World Darts Championship in 2006, defeating Ronnie Baxter in the first round before losing to Darren Webster. An ever-present in the UK Open televised finals in Bolton, Gray's run to the semi-finals at the Antwerp Darts Trophy in 2007 saw him earn a Stan James World Matchplay qualifying spot but he lost 10-12 to Kevin Painter in the first round.

Gray had previously come through to win a place at the 2005 Las Vegas Desert Classic, where he overcame American John Kuczynski in the first round before going down to Ray Carver.

He produced a major upset at the 2007 World Grand Prix when he became only the third player in the history of the tournament to defeat Phil Taylor. Despite losing the first two legs of their first round match, Gray then rarely missed his starting double 16 and took five successive legs to move within one of the match. In the fourth leg of the second set, Gray hit back-to-back 180s and finished the match with a double seven to complete the shock result.

Hoping to build on his success over Taylor in Ireland, Gray suffered a disappointing first round exit from the 2008 World Championship, losing 3-2 to Mark Walsh. This was followed up by a disappointing 2008 UK Open, losing 9-4 to Chris Thompson in the third round. However, Gray bounced back in the 2008 Las Vegas Desert Classic, reaching the quarter-finals for the first time in the competition before being defeated by Taylor.

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Wikipedia