Career
A New Zealand international representative player, he has spent most of his career in Britain both playing and coaching. He was a former defence coach of Glasgow Warriors and a former coach at the SRU working in their Scottish Rugby Academy.He is currently joint Head coach of Glasgow Hawks. In his long career he has represented the New Zealand Kiwis within rugby league and New Zealand Māori sides and has played for the Leeds Rhinos, Bradford Northern, Warrington Wolves, Castleford Tigers and Halifax.
County Cup final appearances
Gary Mercer played fullback in Bradford Northern"s 12-12 draw with Castleford in the 1987 Yorkshire Cup final during the 1987-1988 season at Headingley Stadium, Leeds on Saturday Saturday 17 October 1987, and played centre, id est (that is) number 4, in the 11-2 victory over Castleford in the 1987 Yorkshire Cup final replay during the 1987-1988 season at Elland Road, Leeds on Saturday Saturday 31 October 1987.
Regal Trophy final appearances
Gary Mercer played Left-second-row, id est (that is) number 11, in Warrington"s 12-2 victory over Bradford Northern in the 1990-1991 Regal Trophy final during the 1990-1991 season at Headingley Stadium, Leeds on Saturday 12 January 1991. Rugby League
Mercer was also the player-coach at Halifax and Castleford.
Rugby Union
= Glasgow Warriors Mercer switched to Rugby Union and became the defence coach for the Glasgow Warriors from June 2005 to June 2012 leaving the Warriors at the same time as Sean Lineen. While he was there praise was heaped on his defensive coaching.
= Scotland He became the Scotland Under-20 assistant coach and worked with the Under-21 side.He then worked for the Scottish Rugby Academy.
= Yorkshire Carnegie He left the Scottish academy in August 2014 to have a brief spell running Yorkshire Carnegie. = Glasgow Hawks Mercer is now the Head Coach of Glasgow Hawks. He also has twin daughters who are currently living in Noosa, Australia.