Career
Born in Hamilton, McStay played for Celtic from 1979 to 1987. McStay transferred to Huddersfield Town in March 1987 and later played for N ottinghamshire County and Hartlepool United. In 1994, the Scot left Sligo just before the start of the new season after being approached by Celtic to become their youth team coach.
McStay was appointed the head coach of Celtic Reserves in January 2007, and worked in that role at the club until July 2009, when he left to take up the role as manager of Újpest Football Club in Budapest, Hungary.
His assistant at Celtic and at Újpest was Joe McBride. McStay resigned as Head Coach of Újpest in April 2010, and was replaced by Géza Mészöly.
McStay returned to Celtic in April 2010 to take charge of the reserve side again after leaving Újpest, before departing 2 months later. On 25 November 2010, McStay was appointed manager of Ross County.
McStay left the club by mutual consent after less than three months as manager.
McStay was appointed assistant manager of Stockport County in July 2011 by manager Dietmar Hamann. After Hamann"s departure, in November, new manager Jim Gannon kept McStay on as his assistant. McStay took over as manager of Northern League Division One team Celtic Nation in September 2013.
McStay led his side to their first trophy as Celtic Nation on 29 April 2014, defeating Aspatria 3-0 in the Cumberland Cup Final.
McStay went on to lead the side to a second-place finish in the league, and went undefeated in their final 14 league games of the season. However, this was not enough to gain promotion to the Northern Premier League.
Over the following weeks, a financial review was carried out at the club which resulted in many of their players leaving. Matters reached a head in July 2014 when owner Frank Lynch sold the club on to former chairman Steven Skinner.
Amidst the turmoil at the club, McStay resigned.