Stan Ternent, Lee Clark, Simon Grayson and now Robins have left since 2008.
Coming after defeat on the opening day of the season, Robins' exit is unusual, but it's by no means the first surprise departure of a manager in the club's history.
Others include: Herbert Chapman, who left for Arsenal before the third of Town's hat trick of English titles had been completed. He had also been at the helm with Town won the FA Cup in 1922.
Mick Buxton, just before Christmas in 1986 after eight tremendously successful years at the helm in which he won the old Fourth Division Championship and a further promotion to what is now the Championship.
Neil Warnock, who did not sign a new contract after guiding Town to promotion via the play-offs at Wembley in 1995. He was succeeded by Brian Horton. Peter Jackson in May 1999. The extremely popular former captain had guided the club to the Great Escape and competed well in the division after that.
He was replaced by Steve Bruce for the following season but later returned for a second spell in charge in 2003.