Steve Coppell has announced his resignation from Bristol City after two games in charge and retired from football management.
The Robins have appointed Keith Millen as his replacement on a three-year contract with immediate effect.
Coppell joined Bristol City this summer after ending a six-year spell at Reading in 2009, and they were tipped to challenge for promotion with the signing of goalkeeper David James a signal of their intent.
However, they lost their opening game in the Championship 3-0 at home to newly-promoted Millwall at the weekend and were then knocked out of the Carling Cup 3-2 by League Two side Southend on Tuesday, and Coppell feels he cannot take the team any further.
"It is with the deepest regret that I confirm my departure from Bristol City," Coppell told the club's official website. "I have made my decision after very careful consideration and I believe that it is in the best interests of both the club and me personally that we go our separate ways.
"Bristol City is an excellent club, with brilliant support and a chairman with great ambition for the club's future. Whilst I was looking forward to the challenge of leading the players in this season's campaign, unfortunately, it has become clear over recent weeks, that I found I could not, for whatever reason, become passionate about the role and give the commitment the position demands.
"I appreciate that the timing of my departure is not ideal, but I believe it is best for the club to appoint a new manager or indeed appoint Keith Millen, who has a deep knowledge of the club and the squad, at this stage of the season. That individual can then make decisions on signing players before the window closes and work with the squad for the full campaign.
"I am retiring from football management but still feel I have a contribution to make to the game sometime in the future. I would like to sincerely thank the chairman and the board for their understanding and I wish the club and its supporters every success."
Chairman Steve Lansdown added: "Steve's prestigious career as a player, coupled with his experiences and successes as a manager are in no doubt. His footballing pedigree made him our prime target to manage the club early this year.
"It is disappointing for any club to part company with its manager at this stage of the season. However, we respect Steve's decision, one that allows us the opportunity to appoint his successor and give that individual the full season to work with the squad."
Coppell resigned as Manchester City manager in 1996 after just 33 days in the job.