Neil Lennon was on Friday beginning the process of trying to salvage something from Celtic's miserable season after Tony Mowbray's ill-fated nine-month reign came to an end.
The club on Thursday announced Mowbray's departure, less than 24 hours after their heaviest league defeat outside an Old Firm derby for 30 years, the 4-0 thrashing at St Mirren.
The 46-year-old's 13th loss in charge, which left the Hoops 10 points behind Rangers in the Clydesdale Bank Premier League having played two more games, proved the final straw.
Reacting to his departure and that of assistants Mark Venus and Peter Grant, former West Brom boss Mowbray said: "Naturally, I am very disappointed to be leaving Glasgow Celtic.
"I am very proud to have not only managed but also played for a club with such great tradition and that has tremendous roots in football history."
He added: "I would like to offer my sincere thanks to all of the players and also to my staff who supported me so well. Finally, I would like to wish the club every success in the future."
Reserve-team coach and former Celtic captain Neil Lennon was appointed interim manager as the club begin the hunt for a permanent successor.
League Managers' Association chief executive Richard Bevan said: "It is disappointing that Celtic have parted company with Tony despite (him) being in charge for less than a year, especially when taking into account that the club still have a great chance of silverware this season having reached the semi-finals of the Active Nation Scottish Cup."
Chairman John Reid said: "On behalf of the board and everyone at Celtic Football Club, I would like to offer Tony Mowbray my thanks and sincere best wishes for the future.
"During his period here, Tony has always acted with great dignity. We are all disappointed at the way things have gone this season. However, as supporters, we will collectively build again to re-establish the club to its pre-eminent position within Scottish football."
Chief executive Peter Lawwell added: "Tony is a very fine man and someone who I know is passionate about the club he served so well as a player. Clearly, we have had a difficult season and results have not been as we would have hoped.
"Tony is equally disappointed at some of our results this season but, working so closely with him, I know that throughout his period as manager he has always given the club his total and absolute commitment."
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