Following Sunderland's appointment of Martin O'Neill as their new manager, Sports Mole takes a look at the 59-year-old's history as a player and manager.
After moving from Irish league football, a 19-year-old O'Neill joined Nottingham Forest in 1971. During his time at the City ground the midfielder was part of the most successful period in the club's history as the team won a number of honours in the late '70s, including the First Division title and two European Cups.
O'Neill's club career after Forest was erratic as he rarely spent longer than one year at any given club.
During this time O'Neill enjoyed a healthy international career with Northern Ireland as he notched up 64 caps for his country. His proudest achievement was arguably being captain during the 1982 World Cup, in which Ireland reached the quarter-finals.
After beginning his management career with Grantham Town and Shepshed Charterhouse, O'Neill took non-league Wycombe Wanderers into the football league for the first time in 1995.
A brief spell at Norwich City in 1995 saw him leave the club after only six months in charge due to differences with the board.
O'Neill really put his name on the managerial map when he took over at Leicester City in 1995. Two League Cup triumphs in 1997 and 2000 saw European football at Filbert Street, and the club also enjoyed top-half finishes in the Premier League.
Celtic soon offered O'Neill the chance to wrestle SPL superiority back from Old Firm rivals Rangers. In his first season the Irishman won the domestic treble before another two League and Cup successes. He also guided the side to the 2003 UEFA Cup final, which the Bhoys lost to Porto.
O'Neill stepped down from the position in 2005 to care for his wife, who was suffering from cancer.
After a year out from the game, he returned to club management with Aston Villa.
His first season at Villa Park saw the Birmingham side have the longest unbeaten run of any side at the start of the season before a mid-season slump saw them stumble.
They ended the season the way it started with another nine-game unbeaten run, which saw O'Neill named manager of the month for April. They eventually finished 11th, five places higher than the previous campaign.
The next three seasons saw O'Neill cement Villa's standing in the top half of the Premier League. They finished sixth in three consecutive seasons, regularly challenging the English elite and increasing their points haul in each campaign.
The Northern Irishman made a shock departure at the start of last season, reportedly resigning from his position because of a conflict of views with owner Randy Lerner.
Before his appointment at the Stadium of Light he had been linked with international roles with Northern Ireland and England but always hinted that he would prefer a return to club management.