Colchester have sacked manager Wayne Brown following Saturday’s home loss to Grimsby.
The 1-0 defeat left the U’s fourth from bottom in Sky Bet League Two with six points from their first nine games of the season.
The 45-year-old Brown, a former United player, was named interim Colchester boss in January before being handed the role on a permanent basis in May after guiding the team out of relegation trouble.
Chairman Robbie Cowling said in a statement: “I and everyone associated with the club will always be extremely grateful to Wayne Brown for the job he did last season, when he lifted the club from being in the midst of a relegation battle to finishing a very respectable 15th place.
“However, we have decided to act swiftly and decisively following the team’s poor start to this season.
“I accept that many of you will feel I have made a harsh decision, given Wayne’s success last season and given that he has been such an exceptional servant to Colchester United over the years as a player, coach and manager.
“On a personal level I feel that too, but as the club’s chairman I have a duty to make what I believe are the right decisions for the long-term future of Colchester United.
“We thank Wayne for the hard work and attention to detail he has shown in not only his role as head coach, but in all his roles here at the club.”
