#4 Martin O'Neill
The former Northern Ireland international, Martin O'Neill hung up his boots in 1985 and decided to start his new career as a manager in 1987 with Grantham Town. He left the club in 1989 and then had a brief spell at Shepshed Charterhouse, who currently play in the ninth tier of the English football league system.
He moved to Wycombe Wanderers in February 1990 and led the club to the football division for the first time but moved to Norwich City in June 1995, before leaving in December due to differences with the club chairman.
He joined Leicester City, immediately after leaving Norwich City and got them promoted to the Premier League during his first season at the club. He then enjoyed four seasons in the PL with Leicester, before getting relegated back to the Championship in 2000.
Martin O'Neill left Leicester City the following year and joined the Scottish Premier League club, Celtic. He stayed for five seasons at Celtic and won three Scottish Premiership titles. Celtic finished as the UEFA Cup runners-up in 2003, losing to Jose Mourinho's Porto under his leadership.
He then stayed on in the English top-flight for seven more seasons and won the Premier League Manager of the Month award eight times during his stay.
He started managing the Northern Ireland National Team in 2013, and has remained there since then.