Falling 18 points behind leaders and Old Firm rivals Rangers with eight games to go has prompted the club hierarchy to act – after a season of slip-ups, sub-par performances and protests.
Speculation and rumour has been rife on the manager’s future for some time – and the betting markets on his successor have been ever-changing.
We look at who could be stepping in for the former Hibs and Bolton boss as his second spell in charge at Parkhead comes to an end.
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1. Steve Clarke
Scotland manager was linked with the role while at Kilmarnock but stormed to the top of bookmakers' markets a fortnight ago. Has spoken of loyalty to Scotland job and his contentment with role.
Photo: Ian MacNicol
2. Frank Lampard
Out of work after leaving Chelsea, Englishman would renew his midfield rivalry with Steven Gerrard across Glasgow and has been backed by the likes of Harry Redknapp and others.
Photo: TIM KEETON
3. Eddie Howe
Well-rated Englishman is also out of a job after leaving Bournemouth and frequently linked with roles across the country. Celtic may face competition from Premier League clubs if Howe is their choice to pursue as coach and has been a name mentioned regularly throughout the season.
Photo: CLIVE BRUNSKILL
4. John Kennedy
Existing Parkhead assistant John Kennedy will assume control of the team until the end of the season - and with eight games to go and the prospect of Scottish Cup ties to come he leads the betting market though unlikely to be long-term solution.
Photo: Craig Foy - SNS Group