As a player, Martin O'Neill was a hero with Nottingham Forest, who won two European Cups. However, as a manager, O'Neill became a legend at Celtic across two spells with the club.
The Northern Irishman had already managed Wycombe Wanderers, Norwich City, and Leicester City before taking charge of Celtic in the year 2000. He went on to win the Scottish Premier League three times. O'Neill also claimed the Scottish Cup on three occasions and the Scottish League Cup.
European competition was the blemish on his impressive Celtic CV. O'Neill took the Hoops to the final of the UEFA Cup in 2003, but they lost 3-2 after extra-time to Jose Mourinho's FC Porto.
O'Neil left the Scottish Giants in 2005 and went on to manage Aston Villa, Sunderland, the Republic of Ireland, and Forest. His spell at the City Ground in 2019 appeared to be his final managerial role. He has since been working as a pundit on talkSPORT.
Martin O'Neill rescued Celtic from a tricky situation
Celtic began this season on the back of winning four straight Scottish Premiership titles. With Rangers struggling, it looked like more success under Brendan Rodgers was to come. However, it was Heart of Midlothian who took a surprise lead in the division.
Following a 3-1 defeat to Hearts, Rodgers unexpectantly resigned. Tension had been brewing between him and Celtic's hierarchy. This was reflected in a not-so-complimentary club statement. This was a far contrast to the send-off that O'Neil got.
After Celtic's 1-0 win over Dundee, the club posted on social media, "A legend then, a legend now, a legend forever." O'Neill deserves this tribute for steadying the ship back at Celtic.
In his eight games in charge of Celtic on an interim basis, he won seven and lost just once. That defeat came in a Europa League tie against FC Midtjylland. The Hoops are now level on points with Hearts in the Scottish Premiership.
O'Neill could not have left Celtic in a better place, considering the situation he inherited. The new manager, Wilfried Nancy, will owe O'Neill a lot of thanks if he can defeat Hearts this weekend to go top of the league.
Nancy is unproven in European soccer, but has a great reputation in MLS. He won MLS Cup and Leagues Cup with the Columbus Crew. The appointment seems similar to Ange Postecoglou, who also had no notable experience in Europe, but was still a success at Celtic Park.