Millen took the post at Ashton Gate just over a year ago following the shock departure of Steve Coppell. They had a decent enough season, finishing in 15th place with 60 points and there were hopes of progress this season.
That hasnt' materialised. It was evident last week that his position was hardly secure and so it did not come as a surprise, following the heavy defeat at Bloomfield Road, when the announcement came this morning.
He'd been at Bristol City since 1999 when he signed, as a player, from Watford, and at the end of his playing career he became the under-17 coach.
He was appointed assistant manager by Brian Tinnion, a role in which he continued under Gary Johnson after ruling himself out for the manager's job, but accepted the job following the departure of Coppell after a second spell as caretaker.