Kevin Keen has left his position as Colchester United manager following their relegation from League One.
The 49-year-old took charge of the U's on 21 December, but did not achieve his first league win until March.
The team won only five out of 24 games under Keen and relegation was confirmed by Saturday's 3-0 home loss to Burton.
"After a meeting with the owner, Robbie Cowling over the future direction of the club, Kevin Keen has decided to leave," a club statement said.
"Kevin has worked tirelessly to try and turn around the fortunes of the club this season."
Following his departure, assistant manager David Wright will take charge of the final two games of the season.
Keen replaced Tony Humes with the club on an eight-match winless streak in the third tier and it took a further 12 League One games until they tasted victory under the former West Ham coach.
But by that point they were bottom of the table, and despite three further league victories, Keen was unable to save the club from relegation to League Two.
The club struggled for the three previous seasons, finishing 20th, 16th and then needing a final-day victory over Preston to finish 19th last May.
This term they have struggled defensively and having conceded 95 goals, could become the first team to let in 100 in a season since Stockport County (102) in the old First Division in 2001-02.
Meanwhile, Joe Edwards' red card against Burton has been overturned, meaning he will be available for Saturday's game against Barnsley.
by BBC Essex's Glenn Speller
"Kevin Keen was always fighting the odds as Colchester continue down the road of bringing through youth.
"He wasn't the first choice, with the chairman favouring an internal appointment at the time. Given that fact, there was always an inkling of a lack of permanence about it.
"The club from the outside appears to be in turmoil and a massive summer lies ahead."