Colchester have parted with boss Tony Humes by mutual consent after a run of one win in nine League One matches.
The 49-year-old ex-Ipswich defender has left after Tuesday's defeat by bottom club Crewe left the U's one point above the relegation zone.
Colchester have the worst defensive record in the Football League this term, conceding 44 goals in 19 matches.
Humes leaves after almost 15 months in charge, having replaced Joe Dunne at the helm in September 2014.
U's chairman Robbie Cowling told BBC Essex that Humes had suffered "criticism", some of it which had "gone a bit too far".
"We're trying to bring young players through. Tony's been at the club and coached some of those boys since their early teens," Cowling said.
"He felt that his presence at the club now was detrimental to the club and to those boys' careers. We've decided between us and agreed now that's what we go forward with."
Former U's academy boss Humes helped Colchester avoid relegation to League Two last season with a final-day victory over eventually-promoted Preston North End.
The U's started the 2015-16 campaign with a run of eight games without a win, prompting chairman Cowling to release a statement saying he had no "sack the manager pills".
Four consecutive wins in September lifted both the pressure on Humes and the U's up the table, but since then their only victories have come at home to Port Vale and at Wealdstone in the FA Cup.
"I still believe that Tony would be the ideal man to take the club forward," said Cowling.
"Tony has been a massive part of helping us build one of the best academies we've got, he took over the club with one point and kept us up last season against the odds.
"In my view he should still be at the club and we should be talking about building a statue for the guy.
"For me, he's a legend of the club - other people don't see it that way and want to get abusive and they're probably glad that he's lost his job."
Talking about Humes' replacement, Cowling added: "I can't see me going outside the club. We have good people here already."
Humes' assistant Richard Hall and current under-21s boss John McGreal will take charge of Saturday's game at high-flying Burton Albion, assisted by Wayne Brown.
BBC Essex's Glenn Speller
"Tony Humes is a good coach and a decent man, his team play exciting football, but you can't keep shipping goals at the rate they were and Tuesday's loss to Crewe has proved the last straw.
"The road the club is going down with youngsters has its constraints and is difficult to work within.
"The club needs to think hard about the next move as to whether to continue the policy of promoting from within or go outside for a fresh pair of eyes."