Tony Mowbray has left Celtic following Thursday night's 4-0 thrashing at St Mirren, according to reports.
It is believed Mowbray met chief executive Peter Lawwell at the Hoops' Lennoxtown training ground, though the club were refusing to officially confirm or deny their manager's departure.
Thursday evening's humiliating reverse in Paisley means Celtic are 10 points behind Rangers, who also have two games in hand.
It has also been reported that assistant manager Mark Venus and first-team coach Peter Grant have left the club.
The St Mirren loss was the 13th of Mowbray's tenure, which began when he succeeded Gordon Strachan in the summer.
He joined from West Brom, who were understood to have secured around £2million in compensation for his services.